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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Sep. 30, 2011
Registrant Name dei_EntityRegistrantName JANUS INVESTMENT FUND
Central Index Key dei_EntityCentralIndexKey 0000277751
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jan. 26, 2012
Document Effective Date dei_DocumentEffectiveDate Jan. 27, 2012
Prospectus Date rr_ProspectusDate Jan. 27, 2012
Janus Balanced Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Balanced Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Balanced Fund seeks long-term capital growth, consistent with preservation of capital and balanced by current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 94% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 94.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing 35-65% of its assets in equity securities and the remaining assets in fixed-income securities and cash equivalents. The Fund normally invests at least 25% of its assets in fixed-income senior securities. Fixed-income securities may include corporate debt securities, U.S. Government obligations, mortgage-backed securities and other mortgage-related products, and short-term securities. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

In choosing investments for the Fund, the portfolio managers apply a “bottom up” approach with one portfolio manager focusing on the equity portion of the Fund and the other portfolio manager focusing on the fixed-income portion of the Fund. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio managers share day-to-day responsibility for the Fund’s investments.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a balanced portfolio, including common stocks and bonds. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Mortgage-Backed Securities Risk. Mortgage-backed securities tend to be more sensitive to changes in interest rates than other types of securities. Investments in mortgage-backed securities are subject to both extension risk, where borrowers extend the duration of their mortgages in times of rising interest rates, and prepayment risk, where borrowers pay off their mortgages sooner than expected in times of declining interest rates. These risks may reduce the Fund’s returns. In addition, investments in mortgage-backed securities, including those comprised of subprime mortgages, may be subject to a higher degree of credit risk, valuation risk, and liquidity risk than various other types of fixed-income securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

High-Yield/High-Risk Bond Risk. High-yield/high-risk bonds may be more sensitive than other types of bonds to economic changes, political changes, or adverse developments specific to the company that issued the bond, which may adversely affect their value.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Third Quarter 2009  10.97%                    Worst Quarter:  Third Quarter 2011  -11.05%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The Balanced Index is an internally-calculated, hypothetical combination of unmanaged indices that combines total returns from the S&P 500® Index (55%) and the Barclays Capital U.S. Aggregate Bond Index (45%).

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.12%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.92%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 663
3 Years rr_ExpenseExampleYear03 851
5 Years rr_ExpenseExampleYear05 1,055
10 Years rr_ExpenseExampleYear10 1,641
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 663
3 Years rr_ExpenseExampleNoRedemptionYear03 851
5 Years rr_ExpenseExampleNoRedemptionYear05 1,055
10 Years rr_ExpenseExampleNoRedemptionYear10 1,641
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.66%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 269
3 Years rr_ExpenseExampleYear03 523
5 Years rr_ExpenseExampleYear05 902
10 Years rr_ExpenseExampleYear10 1,965
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 169
3 Years rr_ExpenseExampleNoRedemptionYear03 523
5 Years rr_ExpenseExampleNoRedemptionYear05 902
10 Years rr_ExpenseExampleNoRedemptionYear10 1,965
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.09%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 111
3 Years rr_ExpenseExampleYear03 347
5 Years rr_ExpenseExampleYear05 601
10 Years rr_ExpenseExampleYear10 1,329
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 111
3 Years rr_ExpenseExampleNoRedemptionYear03 347
5 Years rr_ExpenseExampleNoRedemptionYear05 601
10 Years rr_ExpenseExampleNoRedemptionYear10 1,329
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.08%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.63%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 64
3 Years rr_ExpenseExampleYear03 202
5 Years rr_ExpenseExampleYear05 351
10 Years rr_ExpenseExampleYear10 786
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 64
3 Years rr_ExpenseExampleNoRedemptionYear03 202
5 Years rr_ExpenseExampleNoRedemptionYear05 351
10 Years rr_ExpenseExampleNoRedemptionYear10 786
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.34%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 136
3 Years rr_ExpenseExampleYear03 425
5 Years rr_ExpenseExampleYear05 734
10 Years rr_ExpenseExampleYear10 1,613
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 136
3 Years rr_ExpenseExampleNoRedemptionYear03 425
5 Years rr_ExpenseExampleNoRedemptionYear05 734
10 Years rr_ExpenseExampleNoRedemptionYear10 1,613
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.84%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 86
3 Years rr_ExpenseExampleYear03 268
5 Years rr_ExpenseExampleYear05 466
10 Years rr_ExpenseExampleYear10 1,037
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 86
3 Years rr_ExpenseExampleNoRedemptionYear03 268
5 Years rr_ExpenseExampleNoRedemptionYear05 466
10 Years rr_ExpenseExampleNoRedemptionYear10 1,037
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (6.56%)
2003 rr_AnnualReturn2003 13.74%
2004 rr_AnnualReturn2004 8.71%
2005 rr_AnnualReturn2005 7.75%
2006 rr_AnnualReturn2006 10.56%
2007 rr_AnnualReturn2007 10.15%
2008 rr_AnnualReturn2008 (15.22%)
2009 rr_AnnualReturn2009 24.28%
2010 rr_AnnualReturn2010 7.75%
2011 rr_AnnualReturn2011 1.31%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 10.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (11.05%)
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (4.61%)
5 Years rr_AverageAnnualReturnYear05 3.55%
10 Years rr_AverageAnnualReturnYear10 5.05%
Since Inception rr_AverageAnnualReturnSinceInception 9.20%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (0.48%)
5 Years rr_AverageAnnualReturnYear05 4.02%
10 Years rr_AverageAnnualReturnYear10 4.90%
Since Inception rr_AverageAnnualReturnSinceInception 8.89%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.07%
5 Years rr_AverageAnnualReturnYear05 4.58%
10 Years rr_AverageAnnualReturnYear10 5.45%
Since Inception rr_AverageAnnualReturnSinceInception 9.37%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.49%
5 Years rr_AverageAnnualReturnYear05 4.85%
10 Years rr_AverageAnnualReturnYear10 5.72%
Since Inception rr_AverageAnnualReturnSinceInception 9.56%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.80%
5 Years rr_AverageAnnualReturnYear05 4.31%
10 Years rr_AverageAnnualReturnYear10 5.19%
Since Inception rr_AverageAnnualReturnSinceInception 9.16%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.31%
5 Years rr_AverageAnnualReturnYear05 4.85%
10 Years rr_AverageAnnualReturnYear10 5.72%
Since Inception rr_AverageAnnualReturnSinceInception 9.56%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.50%
5 Years rr_AverageAnnualReturnYear05 3.85%
10 Years rr_AverageAnnualReturnYear10 4.88%
Since Inception rr_AverageAnnualReturnSinceInception 8.06%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 1.34%
5 Years rr_AverageAnnualReturnYear05 3.82%
10 Years rr_AverageAnnualReturnYear10 4.61%
Since Inception rr_AverageAnnualReturnSinceInception 7.70%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 7.99%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Barclays Capital U.S. Aggregate Bond Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays Capital U.S. Aggregate Bond Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 7.84%
5 Years rr_AverageAnnualReturnYear05 6.50%
10 Years rr_AverageAnnualReturnYear10 5.78%
Since Inception rr_AverageAnnualReturnSinceInception 6.40%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class A, C, S, I, R, T Shares | Balanced Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Balanced Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.99%
5 Years rr_AverageAnnualReturnYear05 3.14%
10 Years rr_AverageAnnualReturnYear10 4.56%
Since Inception rr_AverageAnnualReturnSinceInception 7.61%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Balanced Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Balanced Fund seeks long-term capital growth, consistent with preservation of capital and balanced by current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 94% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 94.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing 35-65% of its assets in equity securities and the remaining assets in fixed-income securities and cash equivalents. The Fund normally invests at least 25% of its assets in fixed-income senior securities. Fixed-income securities may include corporate debt securities, U.S. Government obligations, mortgage-backed securities and other mortgage-related products, and short-term securities. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

In choosing investments for the Fund, the portfolio managers apply a “bottom up” approach with one portfolio manager focusing on the equity portion of the Fund and the other portfolio manager focusing on the fixed-income portion of the Fund. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio managers share day-to-day responsibility for the Fund’s investments.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a balanced portfolio, including common stocks and bonds. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Mortgage-Backed Securities Risk. Mortgage-backed securities tend to be more sensitive to changes in interest rates than other types of securities. Investments in mortgage-backed securities are subject to both extension risk, where borrowers extend the duration of their mortgages in times of rising interest rates, and prepayment risk, where borrowers pay off their mortgages sooner than expected in times of declining interest rates. These risks may reduce the Fund’s returns. In addition, investments in mortgage-backed securities, including those comprised of subprime mortgages, may be subject to a higher degree of credit risk, valuation risk, and liquidity risk than various other types of fixed-income securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

High-Yield/High-Risk Bond Risk. High-yield/high-risk bonds may be more sensitive than other types of bonds to economic changes, political changes, or adverse developments specific to the company that issued the bond, which may adversely affect their value.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Third Quarter 2009 10.97%          Worst Quarter: Third Quarter 2011 -11.02%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The Balanced Index is an internally-calculated, hypothetical combination of unmanaged indices that combines total returns from the S&P 500® Index (55%) and the Barclays Capital U.S. Aggregate Bond Index (45%).

After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Balanced Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.55%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.73%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 75
3 Years rr_ExpenseExampleYear03 233
5 Years rr_ExpenseExampleYear05 406
10 Years rr_ExpenseExampleYear10 906
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (6.56%)
2003 rr_AnnualReturn2003 13.74%
2004 rr_AnnualReturn2004 8.71%
2005 rr_AnnualReturn2005 7.75%
2006 rr_AnnualReturn2006 10.56%
2007 rr_AnnualReturn2007 10.15%
2008 rr_AnnualReturn2008 (15.22%)
2009 rr_AnnualReturn2009 24.28%
2010 rr_AnnualReturn2010 7.83%
2011 rr_AnnualReturn2011 1.44%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 10.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (11.02%)
Janus Balanced Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.44%
5 Years rr_AverageAnnualReturnYear05 4.89%
10 Years rr_AverageAnnualReturnYear10 5.74%
Since Inception rr_AverageAnnualReturnSinceInception 9.57%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.61%
5 Years rr_AverageAnnualReturnYear05 3.89%
10 Years rr_AverageAnnualReturnYear10 4.90%
Since Inception rr_AverageAnnualReturnSinceInception 8.07%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 1.44%
5 Years rr_AverageAnnualReturnYear05 3.85%
10 Years rr_AverageAnnualReturnYear10 4.63%
Since Inception rr_AverageAnnualReturnSinceInception 7.71%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 7.99%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares | Barclays Capital U.S. Aggregate Bond Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays Capital U.S. Aggregate Bond Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 7.84%
5 Years rr_AverageAnnualReturnYear05 6.50%
10 Years rr_AverageAnnualReturnYear10 5.78%
Since Inception rr_AverageAnnualReturnSinceInception 6.40%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Balanced Fund | Class D Shares | Balanced Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Balanced Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.99%
5 Years rr_AverageAnnualReturnYear05 3.14%
10 Years rr_AverageAnnualReturnYear10 4.56%
Since Inception rr_AverageAnnualReturnSinceInception 7.61%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Contrarian Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Contrarian Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Contrarian Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 130% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 130.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities with the potential for long-term growth of capital. The portfolio manager emphasizes investments in companies with attractive price/free cash flow, which is the relationship between the price of a stock and the company’s available cash from operations, minus capital expenditures. The portfolio manager will typically seek attractively valued companies that are improving their free cash flow and returns on invested capital. Such companies may also include special situations companies that are experiencing management changes and/or are currently out of favor. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Value Investing Risk. Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “value” stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Second Quarter 2009  30.97%                    Worst Quarter:  Fourth Quarter 2008  -27.53%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 663
3 Years rr_ExpenseExampleYear03 848
5 Years rr_ExpenseExampleYear05 1,050
10 Years rr_ExpenseExampleYear10 1,630
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 663
3 Years rr_ExpenseExampleNoRedemptionYear03 848
5 Years rr_ExpenseExampleNoRedemptionYear05 1,050
10 Years rr_ExpenseExampleNoRedemptionYear10 1,630
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.16%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.63%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 266
3 Years rr_ExpenseExampleYear03 514
5 Years rr_ExpenseExampleYear05 887
10 Years rr_ExpenseExampleYear10 1,933
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 166
3 Years rr_ExpenseExampleNoRedemptionYear03 514
5 Years rr_ExpenseExampleNoRedemptionYear05 887
10 Years rr_ExpenseExampleNoRedemptionYear10 1,933
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.35%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.33%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.07%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 109
3 Years rr_ExpenseExampleYear03 340
5 Years rr_ExpenseExampleYear05 590
10 Years rr_ExpenseExampleYear10 1,306
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 109
3 Years rr_ExpenseExampleNoRedemptionYear03 340
5 Years rr_ExpenseExampleNoRedemptionYear05 590
10 Years rr_ExpenseExampleNoRedemptionYear10 1,306
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.19%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.66%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 67
3 Years rr_ExpenseExampleYear03 211
5 Years rr_ExpenseExampleYear05 368
10 Years rr_ExpenseExampleYear10 822
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 67
3 Years rr_ExpenseExampleNoRedemptionYear03 211
5 Years rr_ExpenseExampleNoRedemptionYear05 368
10 Years rr_ExpenseExampleNoRedemptionYear10 822
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.34%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.31%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 133
3 Years rr_ExpenseExampleYear03 415
5 Years rr_ExpenseExampleYear05 718
10 Years rr_ExpenseExampleYear10 1,579
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 133
3 Years rr_ExpenseExampleNoRedemptionYear03 415
5 Years rr_ExpenseExampleNoRedemptionYear05 718
10 Years rr_ExpenseExampleNoRedemptionYear10 1,579
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.47%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.35%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.33%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.82%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 84
3 Years rr_ExpenseExampleYear03 262
5 Years rr_ExpenseExampleYear05 455
10 Years rr_ExpenseExampleYear10 1,014
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 84
3 Years rr_ExpenseExampleNoRedemptionYear03 262
5 Years rr_ExpenseExampleNoRedemptionYear05 455
10 Years rr_ExpenseExampleNoRedemptionYear10 1,014
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (23.70%)
2003 rr_AnnualReturn2003 53.26%
2004 rr_AnnualReturn2004 22.61%
2005 rr_AnnualReturn2005 16.02%
2006 rr_AnnualReturn2006 24.58%
2007 rr_AnnualReturn2007 21.22%
2008 rr_AnnualReturn2008 (48.11%)
2009 rr_AnnualReturn2009 37.02%
2010 rr_AnnualReturn2010 11.16%
2011 rr_AnnualReturn2011 (15.86%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 30.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.53%)
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (20.71%)
5 Years rr_AverageAnnualReturnYear05 (5.48%)
10 Years rr_AverageAnnualReturnYear10 4.51%
Since Inception rr_AverageAnnualReturnSinceInception 3.33%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (17.36%)
5 Years rr_AverageAnnualReturnYear05 (5.09%)
10 Years rr_AverageAnnualReturnYear10 4.33%
Since Inception rr_AverageAnnualReturnSinceInception 3.07%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (16.08%)
5 Years rr_AverageAnnualReturnYear05 (4.53%)
10 Years rr_AverageAnnualReturnYear10 4.92%
Since Inception rr_AverageAnnualReturnSinceInception 3.64%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (15.73%)
5 Years rr_AverageAnnualReturnYear05 (4.22%)
10 Years rr_AverageAnnualReturnYear10 5.27%
Since Inception rr_AverageAnnualReturnSinceInception 3.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (16.29%)
5 Years rr_AverageAnnualReturnYear05 (4.78%)
10 Years rr_AverageAnnualReturnYear10 4.65%
Since Inception rr_AverageAnnualReturnSinceInception 3.38%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (15.86%)
5 Years rr_AverageAnnualReturnYear05 (4.22%)
10 Years rr_AverageAnnualReturnYear10 5.27%
Since Inception rr_AverageAnnualReturnSinceInception 3.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (15.86%)
5 Years rr_AverageAnnualReturnYear05 (4.49%)
10 Years rr_AverageAnnualReturnYear10 4.90%
Since Inception rr_AverageAnnualReturnSinceInception 3.59%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (10.31%)
5 Years rr_AverageAnnualReturnYear05 (3.51%)
10 Years rr_AverageAnnualReturnYear10 4.65%
Since Inception rr_AverageAnnualReturnSinceInception 3.45%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.16%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 1.18%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Contrarian Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Contrarian Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 130% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 130.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities with the potential for long-term growth of capital. The portfolio manager emphasizes investments in companies with attractive price/free cash flow, which is the relationship between the price of a stock and the company’s available cash from operations, minus capital expenditures. The portfolio manager will typically seek attractively valued companies that are improving their free cash flow and returns on invested capital. Such companies may also include special situations companies that are experiencing management changes and/or are currently out of favor. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Value Investing Risk. Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “value” stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 30.97%           Worst Quarter: Fourth Quarter 2008 -27.53%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Contrarian Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.47%
Other Expenses rr_OtherExpensesOverAssets 0.23%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.02%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.70%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 72
3 Years rr_ExpenseExampleYear03 224
5 Years rr_ExpenseExampleYear05 390
10 Years rr_ExpenseExampleYear10 871
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (23.70%)
2003 rr_AnnualReturn2003 53.26%
2004 rr_AnnualReturn2004 22.61%
2005 rr_AnnualReturn2005 16.02%
2006 rr_AnnualReturn2006 24.58%
2007 rr_AnnualReturn2007 21.22%
2008 rr_AnnualReturn2008 (48.11%)
2009 rr_AnnualReturn2009 37.02%
2010 rr_AnnualReturn2010 11.25%
2011 rr_AnnualReturn2011 (15.78%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 30.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.53%)
Janus Contrarian Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (15.78%)
5 Years rr_AverageAnnualReturnYear05 (4.18%)
10 Years rr_AverageAnnualReturnYear10 5.28%
Since Inception rr_AverageAnnualReturnSinceInception 4.00%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (15.79%)
5 Years rr_AverageAnnualReturnYear05 (4.46%)
10 Years rr_AverageAnnualReturnYear10 4.92%
Since Inception rr_AverageAnnualReturnSinceInception 3.61%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (10.26%)
5 Years rr_AverageAnnualReturnYear05 (3.48%)
10 Years rr_AverageAnnualReturnYear10 4.66%
Since Inception rr_AverageAnnualReturnSinceInception 3.46%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.16%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Contrarian Fund | Class D Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 1.18%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2000
Janus Enterprise Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Enterprise Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Enterprise Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 19.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential, and normally invests at least 50% of its equity assets in medium-sized companies. Medium-sized companies are those whose market capitalization falls within the range of companies in the Russell Midcap® Growth Index. Market capitalization is a commonly used measure of the size and value of a company. The market capitalizations within the index will vary, but as of September 30, 2011, they ranged from approximately $107 million to $19.2 billion. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Mid-Sized Companies Risk. The Fund’s investments in securities issued by mid-sized companies may involve greater risks than are customarily associated with larger, more established companies. Securities issued by mid-sized companies tend to be more volatile than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 21.55%              Worst Quarter: Fourth Quarter 2008 -28.79%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.06%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 677
3 Years rr_ExpenseExampleYear03 893
5 Years rr_ExpenseExampleYear05 1,126
10 Years rr_ExpenseExampleYear10 1,795
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 677
3 Years rr_ExpenseExampleNoRedemptionYear03 893
5 Years rr_ExpenseExampleNoRedemptionYear05 1,126
10 Years rr_ExpenseExampleNoRedemptionYear10 1,795
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.78%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 281
3 Years rr_ExpenseExampleYear03 560
5 Years rr_ExpenseExampleYear05 964
10 Years rr_ExpenseExampleYear10 2,095
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 181
3 Years rr_ExpenseExampleNoRedemptionYear03 560
5 Years rr_ExpenseExampleNoRedemptionYear05 964
10 Years rr_ExpenseExampleNoRedemptionYear10 2,095
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.19%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 121
3 Years rr_ExpenseExampleYear03 378
5 Years rr_ExpenseExampleYear05 654
10 Years rr_ExpenseExampleYear10 1,443
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 121
3 Years rr_ExpenseExampleNoRedemptionYear03 378
5 Years rr_ExpenseExampleNoRedemptionYear05 654
10 Years rr_ExpenseExampleNoRedemptionYear10 1,443
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.09%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.73%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 75
3 Years rr_ExpenseExampleYear03 233
5 Years rr_ExpenseExampleYear05 406
10 Years rr_ExpenseExampleYear10 906
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 75
3 Years rr_ExpenseExampleNoRedemptionYear03 233
5 Years rr_ExpenseExampleNoRedemptionYear05 406
10 Years rr_ExpenseExampleNoRedemptionYear10 906
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.44%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 147
3 Years rr_ExpenseExampleYear03 456
5 Years rr_ExpenseExampleYear05 787
10 Years rr_ExpenseExampleYear10 1,724
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 147
3 Years rr_ExpenseExampleNoRedemptionYear03 456
5 Years rr_ExpenseExampleNoRedemptionYear05 787
10 Years rr_ExpenseExampleNoRedemptionYear10 1,724
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.94%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 96
3 Years rr_ExpenseExampleYear03 300
5 Years rr_ExpenseExampleYear05 520
10 Years rr_ExpenseExampleYear10 1,155
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 96
3 Years rr_ExpenseExampleNoRedemptionYear03 300
5 Years rr_ExpenseExampleNoRedemptionYear05 520
10 Years rr_ExpenseExampleNoRedemptionYear10 1,155
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (28.28%)
2003 rr_AnnualReturn2003 35.82%
2004 rr_AnnualReturn2004 20.69%
2005 rr_AnnualReturn2005 11.40%
2006 rr_AnnualReturn2006 13.22%
2007 rr_AnnualReturn2007 21.81%
2008 rr_AnnualReturn2008 (43.13%)
2009 rr_AnnualReturn2009 42.90%
2010 rr_AnnualReturn2010 25.82%
2011 rr_AnnualReturn2011 (1.86%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.55%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (28.79%)
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (7.58%)
5 Years rr_AverageAnnualReturnYear05 2.77%
10 Years rr_AverageAnnualReturnYear10 5.42%
Since Inception rr_AverageAnnualReturnSinceInception 9.10%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (3.63%)
5 Years rr_AverageAnnualReturnYear05 3.19%
10 Years rr_AverageAnnualReturnYear10 5.23%
Since Inception rr_AverageAnnualReturnSinceInception 8.65%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.11%)
5 Years rr_AverageAnnualReturnYear05 3.83%
10 Years rr_AverageAnnualReturnYear10 5.87%
Since Inception rr_AverageAnnualReturnSinceInception 9.28%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.65%)
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 6.13%
Since Inception rr_AverageAnnualReturnSinceInception 9.50%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.35%)
5 Years rr_AverageAnnualReturnYear05 3.57%
10 Years rr_AverageAnnualReturnYear10 5.61%
Since Inception rr_AverageAnnualReturnSinceInception 9.03%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.86%)
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 6.13%
Since Inception rr_AverageAnnualReturnSinceInception 9.50%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (1.86%)
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 6.13%
Since Inception rr_AverageAnnualReturnSinceInception 8.87%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (1.21%)
5 Years rr_AverageAnnualReturnYear05 3.52%
10 Years rr_AverageAnnualReturnYear10 5.39%
Since Inception rr_AverageAnnualReturnSinceInception 8.29%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class A, C, S, I, R, T Shares | Russell Midcap® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell Midcap® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.65%)
5 Years rr_AverageAnnualReturnYear05 2.44%
10 Years rr_AverageAnnualReturnYear10 5.29%
Since Inception rr_AverageAnnualReturnSinceInception 8.72%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Enterprise Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Enterprise Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 19.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential, and normally invests at least 50% of its equity assets in medium-sized companies. Medium-sized companies are those whose market capitalization falls within the range of companies in the Russell Midcap® Growth Index. Market capitalization is a commonly used measure of the size and value of a company. The market capitalizations within the index will vary, but as of September 30, 2011, they ranged from approximately $107 million to $19.2 billion. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Mid-Sized Companies Risk. The Fund’s investments in securities issued by mid-sized companies may involve greater risks than are customarily associated with larger, more established companies. Securities issued by mid-sized companies tend to be more volatile than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 21.55%           Worst Quarter: Fourth Quarter 2008 -28.79%

Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Enterprise Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.84%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 86
3 Years rr_ExpenseExampleYear03 268
5 Years rr_ExpenseExampleYear05 466
10 Years rr_ExpenseExampleYear10 1,037
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (28.28%)
2003 rr_AnnualReturn2003 35.82%
2004 rr_AnnualReturn2004 20.69%
2005 rr_AnnualReturn2005 11.40%
2006 rr_AnnualReturn2006 13.22%
2007 rr_AnnualReturn2007 21.81%
2008 rr_AnnualReturn2008 (43.13%)
2009 rr_AnnualReturn2009 42.90%
2010 rr_AnnualReturn2010 25.93%
2011 rr_AnnualReturn2011 (1.78%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.55%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (28.79%)
Janus Enterprise Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.78%)
5 Years rr_AverageAnnualReturnYear05 4.13%
10 Years rr_AverageAnnualReturnYear10 6.15%
Since Inception rr_AverageAnnualReturnSinceInception 9.51%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (1.78%)
5 Years rr_AverageAnnualReturnYear05 4.13%
10 Years rr_AverageAnnualReturnYear10 6.15%
Since Inception rr_AverageAnnualReturnSinceInception 8.88%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (1.15%)
5 Years rr_AverageAnnualReturnYear05 3.55%
10 Years rr_AverageAnnualReturnYear10 5.41%
Since Inception rr_AverageAnnualReturnSinceInception 8.30%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Enterprise Fund | Class D Shares | Russell Midcap® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell Midcap® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.65%)
5 Years rr_AverageAnnualReturnYear05 2.44%
10 Years rr_AverageAnnualReturnYear10 5.29%
Since Inception rr_AverageAnnualReturnSinceInception 8.72%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 1992
Janus Forty Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Forty Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Forty Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 51% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 51.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing primarily in a core group of 20-40 common stocks selected for their growth potential. The Fund may invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class S Shares, Class A Shares, Class C Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Forty Fund (“JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class S Shares reflects the performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) from August 1, 2000 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class S Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class A Shares reflects the performance of the JAD predecessor fund’s Class A Shares from September 30, 2004 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class A Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2004, the performance shown for Class A Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class A Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2004 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class C Shares reflects the performance of the JAD predecessor fund’s Class C Shares from September 30, 2002 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class C Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2002, the performance shown for Class C Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class C Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2002 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares reflects the performance of the JAD predecessor fund’s Class I Shares from November 28, 2005 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class I Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to November 28, 2005, the performance shown for Class I Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class I Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to November 28, 2005 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class R Shares reflects the performance of the JAD predecessor fund’s Class R Shares from September 30, 2004 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class R Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2004, the performance shown for Class R Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class R Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2004 was calculated using the fees and expenses of Class R Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class T Shares reflects the performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) from August 1, 2000 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class T Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class I Shares, Class R Shares, and Class T Shares of the Fund had been available during each period prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class S Shares, Class A Shares, Class C Shares, Class I Shares, Class R Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class S Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 20.90%            Worst Quarter: Fourth Quarter 2008 -25.11%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class S Shares for periods following July 6, 2009; for the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) for the periods August 1, 2000 to July 6, 2009; and actual distributions for other classes of shares for periods prior to August 1, 2000. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class S Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class S Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class S Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class S Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.09%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.98%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 669
3 Years rr_ExpenseExampleYear03 869
5 Years rr_ExpenseExampleYear05 1,086
10 Years rr_ExpenseExampleYear10 1,707
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 669
3 Years rr_ExpenseExampleNoRedemptionYear03 869
5 Years rr_ExpenseExampleNoRedemptionYear05 1,086
10 Years rr_ExpenseExampleNoRedemptionYear10 1,707
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.78%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 281
3 Years rr_ExpenseExampleYear03 560
5 Years rr_ExpenseExampleYear05 964
10 Years rr_ExpenseExampleYear10 2,095
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 181
3 Years rr_ExpenseExampleNoRedemptionYear03 560
5 Years rr_ExpenseExampleNoRedemptionYear05 964
10 Years rr_ExpenseExampleNoRedemptionYear10 2,095
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.18%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 120
3 Years rr_ExpenseExampleYear03 375
5 Years rr_ExpenseExampleYear05 649
10 Years rr_ExpenseExampleYear10 1,432
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 120
3 Years rr_ExpenseExampleNoRedemptionYear03 375
5 Years rr_ExpenseExampleNoRedemptionYear05 649
10 Years rr_ExpenseExampleNoRedemptionYear10 1,432
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (15.85%)
2003 rr_AnnualReturn2003 18.92%
2004 rr_AnnualReturn2004 17.64%
2005 rr_AnnualReturn2005 14.60%
2006 rr_AnnualReturn2006 10.18%
2007 rr_AnnualReturn2007 35.57%
2008 rr_AnnualReturn2008 (44.02%)
2009 rr_AnnualReturn2009 43.53%
2010 rr_AnnualReturn2010 5.62%
2011 rr_AnnualReturn2011 (7.32%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 20.90%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.11%)
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.75%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 77
3 Years rr_ExpenseExampleYear03 240
5 Years rr_ExpenseExampleYear05 417
10 Years rr_ExpenseExampleYear10 930
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 77
3 Years rr_ExpenseExampleNoRedemptionYear03 240
5 Years rr_ExpenseExampleNoRedemptionYear05 417
10 Years rr_ExpenseExampleNoRedemptionYear10 930
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.43%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 146
3 Years rr_ExpenseExampleYear03 452
5 Years rr_ExpenseExampleYear05 782
10 Years rr_ExpenseExampleYear10 1,713
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 146
3 Years rr_ExpenseExampleNoRedemptionYear03 452
5 Years rr_ExpenseExampleNoRedemptionYear05 782
10 Years rr_ExpenseExampleNoRedemptionYear10 1,713
Janus Forty Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.93%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 95
3 Years rr_ExpenseExampleYear03 296
5 Years rr_ExpenseExampleYear05 515
10 Years rr_ExpenseExampleYear10 1,143
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 95
3 Years rr_ExpenseExampleNoRedemptionYear03 296
5 Years rr_ExpenseExampleNoRedemptionYear05 515
10 Years rr_ExpenseExampleNoRedemptionYear10 1,143
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (12.45%)
5 Years rr_AverageAnnualReturnYear05 0.31%
10 Years rr_AverageAnnualReturnYear10 4.27%
Since Inception rr_AverageAnnualReturnSinceInception 8.43%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (8.80%)
5 Years rr_AverageAnnualReturnYear05 0.73%
10 Years rr_AverageAnnualReturnYear10 4.14%
Since Inception rr_AverageAnnualReturnSinceInception 8.21%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.32%)
5 Years rr_AverageAnnualReturnYear05 1.29%
10 Years rr_AverageAnnualReturnYear10 4.71%
Since Inception rr_AverageAnnualReturnSinceInception 8.75%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (6.96%)
5 Years rr_AverageAnnualReturnYear05 1.76%
10 Years rr_AverageAnnualReturnYear10 4.71%
Since Inception rr_AverageAnnualReturnSinceInception 8.75%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.58%)
5 Years rr_AverageAnnualReturnYear05 1.03%
10 Years rr_AverageAnnualReturnYear10 4.46%
Since Inception rr_AverageAnnualReturnSinceInception 8.51%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.11%)
5 Years rr_AverageAnnualReturnYear05 1.29%
10 Years rr_AverageAnnualReturnYear10 4.71%
Since Inception rr_AverageAnnualReturnSinceInception 8.75%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (7.36%)
5 Years rr_AverageAnnualReturnYear05 1.12%
10 Years rr_AverageAnnualReturnYear10 4.57%
Since Inception rr_AverageAnnualReturnSinceInception 8.61%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (4.71%)
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 4.09%
Since Inception rr_AverageAnnualReturnSinceInception 7.87%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 5.00%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Forty Fund | Class A, C, S, I, R, T Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 4.07%
Inception Date rr_AverageAnnualReturnInceptionDate May 01, 1997
Janus Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 90% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 90.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. Although the Fund may invest in companies of any size, it generally invests in larger, more established companies. As of September 30, 2011, the Fund’s weighted average market capitalization was $61.7 billion. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Third Quarter 2009 15.95%           Worst Quarter: Fourth Quarter 2008 -21.93%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The Core Growth Index is an internally-calculated, hypothetical combination of unmanaged indices that combines total returns from the Russell 1000® Growth Index (50%) and the S&P 500® Index (50%). This index is used to calculate the performance fee adjustment.

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.23%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.08% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.09% [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.99% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 679
3 Years rr_ExpenseExampleYear03 899
5 Years rr_ExpenseExampleYear05 1,136
10 Years rr_ExpenseExampleYear10 1,816
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 679
3 Years rr_ExpenseExampleNoRedemptionYear03 899
5 Years rr_ExpenseExampleNoRedemptionYear05 1,136
10 Years rr_ExpenseExampleNoRedemptionYear10 1,816
Janus Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.71% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.71% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 274
3 Years rr_ExpenseExampleYear03 539
5 Years rr_ExpenseExampleYear05 928
10 Years rr_ExpenseExampleYear10 2,019
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 174
3 Years rr_ExpenseExampleNoRedemptionYear03 539
5 Years rr_ExpenseExampleNoRedemptionYear05 928
10 Years rr_ExpenseExampleNoRedemptionYear10 2,019
Janus Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.15% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.15% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 117
3 Years rr_ExpenseExampleYear03 365
5 Years rr_ExpenseExampleYear05 633
10 Years rr_ExpenseExampleYear10 1,398
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 117
3 Years rr_ExpenseExampleNoRedemptionYear03 365
5 Years rr_ExpenseExampleNoRedemptionYear05 633
10 Years rr_ExpenseExampleNoRedemptionYear10 1,398
Janus Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.73% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.73% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 75
3 Years rr_ExpenseExampleYear03 233
5 Years rr_ExpenseExampleYear05 406
10 Years rr_ExpenseExampleYear10 906
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 75
3 Years rr_ExpenseExampleNoRedemptionYear03 233
5 Years rr_ExpenseExampleNoRedemptionYear05 406
10 Years rr_ExpenseExampleNoRedemptionYear10 906
Janus Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.28%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.38% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.38% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 140
3 Years rr_ExpenseExampleYear03 437
5 Years rr_ExpenseExampleYear05 755
10 Years rr_ExpenseExampleYear10 1,657
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 140
3 Years rr_ExpenseExampleNoRedemptionYear03 437
5 Years rr_ExpenseExampleNoRedemptionYear05 755
10 Years rr_ExpenseExampleNoRedemptionYear10 1,657
Janus Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.90% [4]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [4]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.90% [4]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 92
3 Years rr_ExpenseExampleYear03 287
5 Years rr_ExpenseExampleYear05 498
10 Years rr_ExpenseExampleYear10 1,108
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 92
3 Years rr_ExpenseExampleNoRedemptionYear03 287
5 Years rr_ExpenseExampleNoRedemptionYear05 498
10 Years rr_ExpenseExampleNoRedemptionYear10 1,108
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (27.56%)
2003 rr_AnnualReturn2003 31.71%
2004 rr_AnnualReturn2004 4.69%
2005 rr_AnnualReturn2005 3.98%
2006 rr_AnnualReturn2006 10.59%
2007 rr_AnnualReturn2007 15.22%
2008 rr_AnnualReturn2008 (39.84%)
2009 rr_AnnualReturn2009 37.30%
2010 rr_AnnualReturn2010 11.21%
2011 rr_AnnualReturn2011 (5.88%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.95%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.93%)
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (11.38%)
5 Years rr_AverageAnnualReturnYear05 (1.28%)
10 Years rr_AverageAnnualReturnYear10 0.71%
Since Inception rr_AverageAnnualReturnSinceInception 11.80%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (7.55%)
5 Years rr_AverageAnnualReturnYear05 (0.82%)
10 Years rr_AverageAnnualReturnYear10 0.60%
Since Inception rr_AverageAnnualReturnSinceInception 11.34%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (6.11%)
5 Years rr_AverageAnnualReturnYear05 (0.32%)
10 Years rr_AverageAnnualReturnYear10 1.08%
Since Inception rr_AverageAnnualReturnSinceInception 11.79%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (5.70%)
5 Years rr_AverageAnnualReturnYear05 (0.07%)
10 Years rr_AverageAnnualReturnYear10 1.36%
Since Inception rr_AverageAnnualReturnSinceInception 11.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (6.37%)
5 Years rr_AverageAnnualReturnYear05 (0.56%)
10 Years rr_AverageAnnualReturnYear10 0.84%
Since Inception rr_AverageAnnualReturnSinceInception 11.60%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (5.88%)
5 Years rr_AverageAnnualReturnYear05 (0.07%)
10 Years rr_AverageAnnualReturnYear10 1.36%
Since Inception rr_AverageAnnualReturnSinceInception 11.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (5.95%)
5 Years rr_AverageAnnualReturnYear05 (0.15%)
10 Years rr_AverageAnnualReturnYear10 1.31%
Since Inception rr_AverageAnnualReturnSinceInception 9.44%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (3.74%)
5 Years rr_AverageAnnualReturnYear05 (0.07%)
10 Years rr_AverageAnnualReturnYear10 1.16%
Since Inception rr_AverageAnnualReturnSinceInception 9.31%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 10.00%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class A, C, S, I, R, T Shares | Core Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Core Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.38%
5 Years rr_AverageAnnualReturnYear05 1.13%
10 Years rr_AverageAnnualReturnYear10 2.78%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 90% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 90.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. Although the Fund may invest in companies of any size, it generally invests in larger, more established companies. As of September 30, 2011, the Fund’s weighted average market capitalization was $61.7 billion. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Third Quarter 2009  15.95%          Worst Quarter:  Fourth Quarter 2008  -21.93%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The Core Growth Index is an internally-calculated, hypothetical combination of unmanaged indices that combines total returns from the Russell 1000® Growth Index (50%) and the S&P 500® Index (50%). This index is used to calculate the performance fee adjustment.

After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.60%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.78%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 80
3 Years rr_ExpenseExampleYear03 249
5 Years rr_ExpenseExampleYear05 433
10 Years rr_ExpenseExampleYear10 966
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (27.56%)
2003 rr_AnnualReturn2003 31.71%
2004 rr_AnnualReturn2004 4.69%
2005 rr_AnnualReturn2005 3.98%
2006 rr_AnnualReturn2006 10.59%
2007 rr_AnnualReturn2007 15.22%
2008 rr_AnnualReturn2008 (39.84%)
2009 rr_AnnualReturn2009 37.30%
2010 rr_AnnualReturn2010 11.31%
2011 rr_AnnualReturn2011 (5.77%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.95%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.93%)
Janus Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (5.77%)
5 Years rr_AverageAnnualReturnYear05 (0.03%)
10 Years rr_AverageAnnualReturnYear10 1.38%
Since Inception rr_AverageAnnualReturnSinceInception 11.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (5.86%)
5 Years rr_AverageAnnualReturnYear05 (0.12%)
10 Years rr_AverageAnnualReturnYear10 1.33%
Since Inception rr_AverageAnnualReturnSinceInception 9.45%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (3.63%)
5 Years rr_AverageAnnualReturnYear05 (0.04%)
10 Years rr_AverageAnnualReturnYear10 1.18%
Since Inception rr_AverageAnnualReturnSinceInception 9.31%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 10.00%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Fund | Class D Shares | Core Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Core Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.38%
5 Years rr_AverageAnnualReturnYear05 1.13%
10 Years rr_AverageAnnualReturnYear10 2.78%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 05, 1970
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Growth and Income Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Growth and Income Fund seeks long-term capital growth and current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 65% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 65.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally emphasizing investments in common stocks. The Fund will normally invest up to 75% of its assets in equity securities selected primarily for their growth potential and at least 25% of its assets in securities the portfolio manager believes have income potential. Eligible equity securities in which the Fund may invest include:

• domestic and foreign common stocks

• preferred stocks

• securities convertible into common stocks or preferred stocks, such as convertible preferred stocks, bonds, and debentures

• other securities with equity characteristics

Equity securities may make up part or all of the income component if they currently pay dividends or the portfolio manager believes they have potential for increasing or commencing dividend payments. The Fund is not designed for investors who need consistent income, and the Fund’s investment strategies could result in significant fluctuations of income.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 18.72%          Worst Quarter: Fourth Quarter 2008 -21.67%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.96% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.01% [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.95% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 667
3 Years rr_ExpenseExampleYear03 863
5 Years rr_ExpenseExampleYear05 1,075
10 Years rr_ExpenseExampleYear10 1,685
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 667
3 Years rr_ExpenseExampleNoRedemptionYear03 863
5 Years rr_ExpenseExampleNoRedemptionYear05 1,075
10 Years rr_ExpenseExampleNoRedemptionYear10 1,685
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.10%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.70% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.70% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 273
3 Years rr_ExpenseExampleYear03 536
5 Years rr_ExpenseExampleYear05 923
10 Years rr_ExpenseExampleYear10 2,009
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 173
3 Years rr_ExpenseExampleNoRedemptionYear03 536
5 Years rr_ExpenseExampleNoRedemptionYear05 923
10 Years rr_ExpenseExampleNoRedemptionYear10 2,009
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.15% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.15% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 117
3 Years rr_ExpenseExampleYear03 365
5 Years rr_ExpenseExampleYear05 633
10 Years rr_ExpenseExampleYear10 1,398
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 117
3 Years rr_ExpenseExampleNoRedemptionYear03 365
5 Years rr_ExpenseExampleNoRedemptionYear05 633
10 Years rr_ExpenseExampleNoRedemptionYear10 1,398
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.71% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.01% [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.70% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 73
3 Years rr_ExpenseExampleYear03 227
5 Years rr_ExpenseExampleYear05 395
10 Years rr_ExpenseExampleYear10 883
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 73
3 Years rr_ExpenseExampleNoRedemptionYear03 227
5 Years rr_ExpenseExampleNoRedemptionYear05 395
10 Years rr_ExpenseExampleNoRedemptionYear10 883
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.39% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.39% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 142
3 Years rr_ExpenseExampleYear03 440
5 Years rr_ExpenseExampleYear05 761
10 Years rr_ExpenseExampleYear10 1,669
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 142
3 Years rr_ExpenseExampleNoRedemptionYear03 440
5 Years rr_ExpenseExampleNoRedemptionYear05 761
10 Years rr_ExpenseExampleNoRedemptionYear10 1,669
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.60%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.90% [5]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [5]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.90% [5]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 92
3 Years rr_ExpenseExampleYear03 287
5 Years rr_ExpenseExampleYear05 498
10 Years rr_ExpenseExampleYear10 1,108
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 92
3 Years rr_ExpenseExampleNoRedemptionYear03 287
5 Years rr_ExpenseExampleNoRedemptionYear05 498
10 Years rr_ExpenseExampleNoRedemptionYear10 1,108
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (21.51%)
2003 rr_AnnualReturn2003 24.65%
2004 rr_AnnualReturn2004 11.89%
2005 rr_AnnualReturn2005 12.48%
2006 rr_AnnualReturn2006 7.82%
2007 rr_AnnualReturn2007 8.69%
2008 rr_AnnualReturn2008 (42.48%)
2009 rr_AnnualReturn2009 38.64%
2010 rr_AnnualReturn2010 8.63%
2011 rr_AnnualReturn2011 (1.58%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.72%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.67%)
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (7.26%)
5 Years rr_AverageAnnualReturnYear05 (2.75%)
10 Years rr_AverageAnnualReturnYear10 1.41%
Since Inception rr_AverageAnnualReturnSinceInception 9.09%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (3.36%)
5 Years rr_AverageAnnualReturnYear05 (2.32%)
10 Years rr_AverageAnnualReturnYear10 1.23%
Since Inception rr_AverageAnnualReturnSinceInception 8.68%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.85%)
5 Years rr_AverageAnnualReturnYear05 (1.79%)
10 Years rr_AverageAnnualReturnYear10 1.80%
Since Inception rr_AverageAnnualReturnSinceInception 9.24%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.40%)
5 Years rr_AverageAnnualReturnYear05 (1.51%)
10 Years rr_AverageAnnualReturnYear10 2.09%
Since Inception rr_AverageAnnualReturnSinceInception 9.46%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.06%)
5 Years rr_AverageAnnualReturnYear05 (2.03%)
10 Years rr_AverageAnnualReturnYear10 1.55%
Since Inception rr_AverageAnnualReturnSinceInception 9.00%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.58%)
5 Years rr_AverageAnnualReturnYear05 (1.51%)
10 Years rr_AverageAnnualReturnYear10 2.09%
Since Inception rr_AverageAnnualReturnSinceInception 9.46%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (1.73%)
5 Years rr_AverageAnnualReturnYear05 (2.09%)
10 Years rr_AverageAnnualReturnYear10 1.70%
Since Inception rr_AverageAnnualReturnSinceInception 8.41%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (0.82%)
5 Years rr_AverageAnnualReturnYear05 (1.32%)
10 Years rr_AverageAnnualReturnYear10 1.74%
Since Inception rr_AverageAnnualReturnSinceInception 8.08%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 8.32%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class A, C, S, I, R, T Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 7.42%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Growth and Income Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Growth and Income Fund seeks long-term capital growth and current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 65% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 65.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally emphasizing investments in common stocks. The Fund will normally invest up to 75% of its assets in equity securities selected primarily for their growth potential and at least 25% of its assets in securities the portfolio manager believes have income potential. Eligible equity securities in which the Fund may invest include:

• domestic and foreign common stocks

• preferred stocks

• securities convertible into common stocks or preferred stocks, such as convertible preferred stocks, bonds, and debentures

• other securities with equity characteristics

Equity securities may make up part or all of the income component if they currently pay dividends or the portfolio manager believes they have potential for increasing or commencing dividend payments. The Fund is not designed for investors who need consistent income, and the Fund’s investment strategies could result in significant fluctuations of income.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Second Quarter 2009  18.72%          Worst Quarter:  Fourth Quarter 2008  -21.67%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Growth and Income Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.60%
Other Expenses rr_OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.80%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 82
3 Years rr_ExpenseExampleYear03 255
5 Years rr_ExpenseExampleYear05 444
10 Years rr_ExpenseExampleYear10 990
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (21.51%)
2003 rr_AnnualReturn2003 24.65%
2004 rr_AnnualReturn2004 11.89%
2005 rr_AnnualReturn2005 12.48%
2006 rr_AnnualReturn2006 7.82%
2007 rr_AnnualReturn2007 8.69%
2008 rr_AnnualReturn2008 (42.48%)
2009 rr_AnnualReturn2009 38.64%
2010 rr_AnnualReturn2010 8.72%
2011 rr_AnnualReturn2011 (1.47%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.72%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.67%)
Janus Growth and Income Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.47%)
5 Years rr_AverageAnnualReturnYear05 (1.47%)
10 Years rr_AverageAnnualReturnYear10 2.11%
Since Inception rr_AverageAnnualReturnSinceInception 9.47%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (1.64%)
5 Years rr_AverageAnnualReturnYear05 (2.06%)
10 Years rr_AverageAnnualReturnYear10 1.71%
Since Inception rr_AverageAnnualReturnSinceInception 8.41%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (0.73%)
5 Years rr_AverageAnnualReturnYear05 (1.29%)
10 Years rr_AverageAnnualReturnYear10 1.75%
Since Inception rr_AverageAnnualReturnSinceInception 8.09%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 8.32%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Growth and Income Fund | Class D Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 7.42%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Research Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Research Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Research Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 88% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 88.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. The Fund may invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

Janus Capital’s equity research analysts (the “Research Team”) select investments for the Fund. The Research Team, comprised of sector specialists, conducts fundamental analysis with a focus on “bottom up” research, quantitative modeling, and valuation analysis. Using this research process, analysts rate their stocks based upon attractiveness. Analysts bring their high-conviction ideas to their respective sector teams. Sector teams compare the appreciation and risk potential of each of the team’s high-conviction ideas and construct a sector portfolio that is intended to maximize the best risk-reward opportunities. Although the Research Team may find high-conviction investment ideas anywhere in the world, the Research Team may emphasize investments in securities of U.S.-based issuers.

Positions may be sold when, among other things, there is no longer high conviction in the return potential of the investment or if the risk characteristics have caused a re-evaluation of the opportunity. This may occur if the stock has appreciated and reflects the anticipated value, if another company represents a better risk-reward opportunity, or if the investment’s fundamental characteristics deteriorate. Securities may also be sold from the portfolio to rebalance sector weightings.

Janus Capital’s Director of Equity Research oversees the investment process and is responsible for the day-to-day management of the Fund. It is expected that the Fund will be broadly diversified among a variety of industry sectors. The Fund intends to be fully invested under normal circumstances. However, under unusual circumstances, if the Research Team does not have high conviction in enough investment opportunities, the Fund’s uninvested assets may be held in cash or similar instruments.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the investment personnel’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the investment personnel’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities. The Fund compares and broadly matches its sector weights to those of a growth-based index. If growth stocks are out of favor, sectors that are larger in a growth index may underperform, leading to Fund underperformance relative to indices less biased toward growth stocks.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 22.23%          Worst Quarter: Fourth Quarter 2008 -25.30%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Research Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.57%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.09%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 663
3 Years rr_ExpenseExampleYear03 848
5 Years rr_ExpenseExampleYear05 1,050
10 Years rr_ExpenseExampleYear10 1,630
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 663
3 Years rr_ExpenseExampleNoRedemptionYear03 848
5 Years rr_ExpenseExampleNoRedemptionYear05 1,050
10 Years rr_ExpenseExampleNoRedemptionYear10 1,630
Janus Research Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.57%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.68%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 271
3 Years rr_ExpenseExampleYear03 530
5 Years rr_ExpenseExampleYear05 913
10 Years rr_ExpenseExampleYear10 1,987
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 171
3 Years rr_ExpenseExampleNoRedemptionYear03 530
5 Years rr_ExpenseExampleNoRedemptionYear05 913
10 Years rr_ExpenseExampleNoRedemptionYear10 1,987
Janus Research Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.57%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.11%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 113
3 Years rr_ExpenseExampleYear03 353
5 Years rr_ExpenseExampleYear05 612
10 Years rr_ExpenseExampleYear10 1,352
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 113
3 Years rr_ExpenseExampleNoRedemptionYear03 353
5 Years rr_ExpenseExampleNoRedemptionYear05 612
10 Years rr_ExpenseExampleNoRedemptionYear10 1,352
Janus Research Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.57%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.68%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 69
3 Years rr_ExpenseExampleYear03 218
5 Years rr_ExpenseExampleYear05 379
10 Years rr_ExpenseExampleYear10 847
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 69
3 Years rr_ExpenseExampleNoRedemptionYear03 218
5 Years rr_ExpenseExampleNoRedemptionYear05 379
10 Years rr_ExpenseExampleNoRedemptionYear10 847
Janus Research Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.57%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.88%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 90
3 Years rr_ExpenseExampleYear03 281
5 Years rr_ExpenseExampleYear05 488
10 Years rr_ExpenseExampleYear10 1,084
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 90
3 Years rr_ExpenseExampleNoRedemptionYear03 281
5 Years rr_ExpenseExampleNoRedemptionYear05 488
10 Years rr_ExpenseExampleNoRedemptionYear10 1,084
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (29.00%)
2003 rr_AnnualReturn2003 32.11%
2004 rr_AnnualReturn2004 10.77%
2005 rr_AnnualReturn2005 6.82%
2006 rr_AnnualReturn2006 8.65%
2007 rr_AnnualReturn2007 24.52%
2008 rr_AnnualReturn2008 (44.36%)
2009 rr_AnnualReturn2009 43.01%
2010 rr_AnnualReturn2010 20.97%
2011 rr_AnnualReturn2011 (3.93%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.23%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.30%)
Janus Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (9.49%)
5 Years rr_AverageAnnualReturnYear05 1.50%
10 Years rr_AverageAnnualReturnYear10 2.51%
Since Inception rr_AverageAnnualReturnSinceInception 9.19%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (5.67%)
5 Years rr_AverageAnnualReturnYear05 1.96%
10 Years rr_AverageAnnualReturnYear10 2.38%
Since Inception rr_AverageAnnualReturnSinceInception 8.79%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.15%)
5 Years rr_AverageAnnualReturnYear05 2.51%
10 Years rr_AverageAnnualReturnYear10 2.95%
Since Inception rr_AverageAnnualReturnSinceInception 9.39%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (3.76%)
5 Years rr_AverageAnnualReturnYear05 2.86%
10 Years rr_AverageAnnualReturnYear10 3.34%
Since Inception rr_AverageAnnualReturnSinceInception 9.76%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (3.93%)
5 Years rr_AverageAnnualReturnYear05 2.86%
10 Years rr_AverageAnnualReturnYear10 3.34%
Since Inception rr_AverageAnnualReturnSinceInception 9.76%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (4.01%)
5 Years rr_AverageAnnualReturnYear05 2.79%
10 Years rr_AverageAnnualReturnYear10 3.29%
Since Inception rr_AverageAnnualReturnSinceInception 8.49%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (2.44%)
5 Years rr_AverageAnnualReturnYear05 2.44%
10 Years rr_AverageAnnualReturnYear10 2.89%
Since Inception rr_AverageAnnualReturnSinceInception 8.09%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 7.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class A, C, S, I, T Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 7.06%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Research Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Research Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 88% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 88.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. The Fund may invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

Janus Capital’s equity research analysts (the “Research Team”) select investments for the Fund. The Research Team, comprised of sector specialists, conducts fundamental analysis with a focus on “bottom up” research, quantitative modeling, and valuation analysis. Using this research process, analysts rate their stocks based upon attractiveness. Analysts bring their high-conviction ideas to their respective sector teams. Sector teams compare the appreciation and risk potential of each of the team’s high-conviction ideas and construct a sector portfolio that is intended to maximize the best risk-reward opportunities. Although the Research Team may find high-conviction investment ideas anywhere in the world, the Research Team may emphasize investments in securities of U.S.-based issuers.

Positions may be sold when, among other things, there is no longer high conviction in the return potential of the investment or if the risk characteristics have caused a re-evaluation of the opportunity. This may occur if the stock has appreciated and reflects the anticipated value, if another company represents a better risk-reward opportunity, or if the investment’s fundamental characteristics deteriorate. Securities may also be sold from the portfolio to rebalance sector weightings.

Janus Capital’s Director of Equity Research oversees the investment process and is responsible for the day-to-day management of the Fund. It is expected that the Fund will be broadly diversified among a variety of industry sectors. The Fund intends to be fully invested under normal circumstances. However, under unusual circumstances, if the Research Team does not have high conviction in enough investment opportunities, the Fund’s uninvested assets may be held in cash or similar instruments.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the investment personnel’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the investment personnel’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities. The Fund compares and broadly matches its sector weights to those of a growth-based index. If growth stocks are out of favor, sectors that are larger in a growth index may underperform, leading to Fund underperformance relative to indices less biased toward growth stocks.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Second Quarter 2009  22.23%          Worst Quarter:  Fourth Quarter 2008  -25.30%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Research Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.57%
Other Expenses rr_OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.77%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 79
3 Years rr_ExpenseExampleYear03 246
5 Years rr_ExpenseExampleYear05 428
10 Years rr_ExpenseExampleYear10 954
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (29.00%)
2003 rr_AnnualReturn2003 32.11%
2004 rr_AnnualReturn2004 10.77%
2005 rr_AnnualReturn2005 6.82%
2006 rr_AnnualReturn2006 8.65%
2007 rr_AnnualReturn2007 24.52%
2008 rr_AnnualReturn2008 (44.36%)
2009 rr_AnnualReturn2009 43.01%
2010 rr_AnnualReturn2010 21.07%
2011 rr_AnnualReturn2011 (3.84%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.23%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.30%)
Janus Research Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (3.84%)
5 Years rr_AverageAnnualReturnYear05 2.90%
10 Years rr_AverageAnnualReturnYear10 3.36%
Since Inception rr_AverageAnnualReturnSinceInception 9.77%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (3.94%)
5 Years rr_AverageAnnualReturnYear05 2.82%
10 Years rr_AverageAnnualReturnYear10 3.31%
Since Inception rr_AverageAnnualReturnSinceInception 8.50%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (2.36%)
5 Years rr_AverageAnnualReturnYear05 2.47%
10 Years rr_AverageAnnualReturnYear10 2.90%
Since Inception rr_AverageAnnualReturnSinceInception 8.10%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 7.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Research Fund | Class D Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 7.06%
Inception Date rr_AverageAnnualReturnInceptionDate May 03, 1993
Janus Triton Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Triton Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Triton Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 42% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 42.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. In pursuing that objective, the Fund invests in equity securities of small- and medium-sized companies. Generally, small- and medium-sized companies have a market capitalization of less than $10 billion. Market capitalization is a commonly used measure of the size and value of a company.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Small- and Mid-Sized Companies Risk. The Fund’s investments in securities issued by small- and mid-sized companies, which tend to be smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. Securities issued by small- and mid-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 24.76%            Worst Quarter: Fourth Quarter 2008 -23.79%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.02%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 673
3 Years rr_ExpenseExampleYear03 881
5 Years rr_ExpenseExampleYear05 1,106
10 Years rr_ExpenseExampleYear10 1,751
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 673
3 Years rr_ExpenseExampleNoRedemptionYear03 881
5 Years rr_ExpenseExampleNoRedemptionYear05 1,106
10 Years rr_ExpenseExampleNoRedemptionYear10 1,751
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.81%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 284
3 Years rr_ExpenseExampleYear03 569
5 Years rr_ExpenseExampleYear05 980
10 Years rr_ExpenseExampleYear10 2,127
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 184
3 Years rr_ExpenseExampleNoRedemptionYear03 569
5 Years rr_ExpenseExampleNoRedemptionYear05 980
10 Years rr_ExpenseExampleNoRedemptionYear10 2,127
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.19%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 121
3 Years rr_ExpenseExampleYear03 378
5 Years rr_ExpenseExampleYear05 654
10 Years rr_ExpenseExampleYear10 1,443
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 121
3 Years rr_ExpenseExampleNoRedemptionYear03 378
5 Years rr_ExpenseExampleNoRedemptionYear05 654
10 Years rr_ExpenseExampleNoRedemptionYear10 1,443
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.12%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.76%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 78
3 Years rr_ExpenseExampleYear03 243
5 Years rr_ExpenseExampleYear05 422
10 Years rr_ExpenseExampleYear10 942
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 78
3 Years rr_ExpenseExampleNoRedemptionYear03 243
5 Years rr_ExpenseExampleNoRedemptionYear05 422
10 Years rr_ExpenseExampleNoRedemptionYear10 942
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.44%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 147
3 Years rr_ExpenseExampleYear03 456
5 Years rr_ExpenseExampleYear05 787
10 Years rr_ExpenseExampleYear10 1,724
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 147
3 Years rr_ExpenseExampleNoRedemptionYear03 456
5 Years rr_ExpenseExampleNoRedemptionYear05 787
10 Years rr_ExpenseExampleNoRedemptionYear10 1,724
Janus Triton Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.94%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 96
3 Years rr_ExpenseExampleYear03 300
5 Years rr_ExpenseExampleYear05 520
10 Years rr_ExpenseExampleYear10 1,155
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 96
3 Years rr_ExpenseExampleNoRedemptionYear03 300
5 Years rr_ExpenseExampleNoRedemptionYear05 520
10 Years rr_ExpenseExampleNoRedemptionYear10 1,155
Annual Total Returns rr_BarChartTableAbstract  
2006 rr_AnnualReturn2006 15.85%
2007 rr_AnnualReturn2007 20.69%
2008 rr_AnnualReturn2008 (40.53%)
2009 rr_AnnualReturn2009 49.99%
2010 rr_AnnualReturn2010 31.40%
2011 rr_AnnualReturn2011 2.60%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 24.76%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.79%)
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (3.41%)
5 Years rr_AverageAnnualReturnYear05 6.30%
Since Inception rr_AverageAnnualReturnSinceInception 9.45%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 0.72%
5 Years rr_AverageAnnualReturnYear05 6.81%
Since Inception rr_AverageAnnualReturnSinceInception 9.60%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.36%
5 Years rr_AverageAnnualReturnYear05 7.38%
Since Inception rr_AverageAnnualReturnSinceInception 10.20%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.77%
5 Years rr_AverageAnnualReturnYear05 7.73%
Since Inception rr_AverageAnnualReturnSinceInception 10.55%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.05%
5 Years rr_AverageAnnualReturnYear05 7.20%
Since Inception rr_AverageAnnualReturnSinceInception 9.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.60%
5 Years rr_AverageAnnualReturnYear05 7.73%
Since Inception rr_AverageAnnualReturnSinceInception 10.55%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 1.99%
5 Years rr_AverageAnnualReturnYear05 6.75%
Since Inception rr_AverageAnnualReturnSinceInception 9.76%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.36%
5 Years rr_AverageAnnualReturnYear05 6.23%
Since Inception rr_AverageAnnualReturnSinceInception 8.91%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Russell 2500™ Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2500TM Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.57%)
5 Years rr_AverageAnnualReturnYear05 2.89%
Since Inception rr_AverageAnnualReturnSinceInception 5.20%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class A, C, S, I, R, T Shares | Russell 2000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.91%)
5 Years rr_AverageAnnualReturnYear05 2.09%
Since Inception rr_AverageAnnualReturnSinceInception 4.41%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Triton Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Triton Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 42% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 42.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. In pursuing that objective, the Fund invests in equity securities of small- and medium-sized companies. Generally, small- and medium-sized companies have a market capitalization of less than $10 billion. Market capitalization is a commonly used measure of the size and value of a company.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Small- and Mid-Sized Companies Risk. The Fund’s investments in securities issued by small- and mid-sized companies, which tend to be smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. Securities issued by small- and mid-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter:  Second Quarter 2009  24.76%          Worst Quarter:  Fourth Quarter 2008  -23.79%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Triton Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.83%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 85
3 Years rr_ExpenseExampleYear03 265
5 Years rr_ExpenseExampleYear05 460
10 Years rr_ExpenseExampleYear10 1,025
Annual Total Returns rr_BarChartTableAbstract  
2006 rr_AnnualReturn2006 15.85%
2007 rr_AnnualReturn2007 20.69%
2008 rr_AnnualReturn2008 (40.53%)
2009 rr_AnnualReturn2009 49.99%
2010 rr_AnnualReturn2010 31.48%
2011 rr_AnnualReturn2011 2.72%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 24.76%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.79%)
Janus Triton Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.72%
5 Years rr_AverageAnnualReturnYear05 7.77%
Since Inception rr_AverageAnnualReturnSinceInception 10.58%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 6.79%
Since Inception rr_AverageAnnualReturnSinceInception 9.79%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 6.26%
Since Inception rr_AverageAnnualReturnSinceInception 8.94%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class D Shares | Russell 2500™ Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2500TM Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.57%)
5 Years rr_AverageAnnualReturnYear05 2.89%
Since Inception rr_AverageAnnualReturnSinceInception 5.20%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Triton Fund | Class D Shares | Russell 2000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.91%)
5 Years rr_AverageAnnualReturnYear05 2.09%
Since Inception rr_AverageAnnualReturnSinceInception 4.41%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Venture Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Venture Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Venture Fund seeks capital appreciation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 81 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 54% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 54.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing at least 50% of its equity assets in small-sized companies. The Fund may also invest in larger companies with strong growth potential or relatively well-known and large companies with potential for capital appreciation. Small-sized companies are defined by the portfolio managers as those companies whose market capitalization falls within the range of companies in the Russell 2000® Growth Index. Market capitalization is a commonly used measure of the size and value of a company. The market capitalizations within the index will vary, but as of September 30, 2011, they ranged from approximately $29 million to $3.7 billion. Companies whose capitalization or revenues fall outside these ranges after the Fund’s initial purchase continue to be considered small-sized.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Small-Sized Companies Risk. The Fund’s investments in securities issued by small-sized companies, which tend to be smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. Securities issued by small-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on May 6, 2011.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to May 6, 2011, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to May 6, 2011, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to May 6, 2011, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 28.30%          Worst Quarter: Fourth Quarter 2008 -28.61%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Venture Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.12%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.01% [6]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [6]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.01% [6]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 672
3 Years rr_ExpenseExampleYear03 878
5 Years rr_ExpenseExampleYear05 1,101
10 Years rr_ExpenseExampleYear10 1,740
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 672
3 Years rr_ExpenseExampleNoRedemptionYear03 878
5 Years rr_ExpenseExampleNoRedemptionYear05 1,101
10 Years rr_ExpenseExampleNoRedemptionYear10 1,740
Janus Venture Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 1.36%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.35%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.00% [6]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.93% [6]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 2.07% [6]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 403
3 Years rr_ExpenseExampleYear03 927
5 Years rr_ExpenseExampleYear05 1,577
10 Years rr_ExpenseExampleYear10 3,318
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 303
3 Years rr_ExpenseExampleNoRedemptionYear03 927
5 Years rr_ExpenseExampleNoRedemptionYear05 1,577
10 Years rr_ExpenseExampleNoRedemptionYear10 3,318
Janus Venture Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.19% [6]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [6]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.19% [6]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 121
3 Years rr_ExpenseExampleYear03 378
5 Years rr_ExpenseExampleYear05 654
10 Years rr_ExpenseExampleYear10 1,443
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 121
3 Years rr_ExpenseExampleNoRedemptionYear03 378
5 Years rr_ExpenseExampleNoRedemptionYear05 654
10 Years rr_ExpenseExampleNoRedemptionYear10 1,443
Janus Venture Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.09%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.08%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.73% [6]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [6]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.73% [6]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 75
3 Years rr_ExpenseExampleYear03 233
5 Years rr_ExpenseExampleYear05 406
10 Years rr_ExpenseExampleYear10 906
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 75
3 Years rr_ExpenseExampleNoRedemptionYear03 233
5 Years rr_ExpenseExampleNoRedemptionYear05 406
10 Years rr_ExpenseExampleNoRedemptionYear10 906
Janus Venture Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.32%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.96% [6]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [6]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.96% [6]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 98
3 Years rr_ExpenseExampleYear03 306
5 Years rr_ExpenseExampleYear05 531
10 Years rr_ExpenseExampleYear10 1,178
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 98
3 Years rr_ExpenseExampleNoRedemptionYear03 306
5 Years rr_ExpenseExampleNoRedemptionYear05 531
10 Years rr_ExpenseExampleNoRedemptionYear10 1,178
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (27.24%)
2003 rr_AnnualReturn2003 55.75%
2004 rr_AnnualReturn2004 17.56%
2005 rr_AnnualReturn2005 1.55%
2006 rr_AnnualReturn2006 23.58%
2007 rr_AnnualReturn2007 16.36%
2008 rr_AnnualReturn2008 (51.43%)
2009 rr_AnnualReturn2009 54.50%
2010 rr_AnnualReturn2010 26.96%
2011 rr_AnnualReturn2011 2.05%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 28.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (28.61%)
Janus Venture Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (4.31%)
5 Years rr_AverageAnnualReturnYear05 1.08%
10 Years rr_AverageAnnualReturnYear10 5.71%
Since Inception rr_AverageAnnualReturnSinceInception 11.10%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (2.24%)
5 Years rr_AverageAnnualReturnYear05 1.41%
10 Years rr_AverageAnnualReturnYear10 5.46%
Since Inception rr_AverageAnnualReturnSinceInception 10.61%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.05%
5 Years rr_AverageAnnualReturnYear05 2.12%
10 Years rr_AverageAnnualReturnYear10 6.17%
Since Inception rr_AverageAnnualReturnSinceInception 11.22%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.05%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 6.58%
Since Inception rr_AverageAnnualReturnSinceInception 11.53%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.05%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 6.58%
Since Inception rr_AverageAnnualReturnSinceInception 11.53%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.94%
5 Years rr_AverageAnnualReturnYear05 1.53%
10 Years rr_AverageAnnualReturnYear10 5.82%
Since Inception rr_AverageAnnualReturnSinceInception 9.38%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.81%
5 Years rr_AverageAnnualReturnYear05 2.03%
10 Years rr_AverageAnnualReturnYear10 5.70%
Since Inception rr_AverageAnnualReturnSinceInception 9.33%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Russell 2000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.91%)
5 Years rr_AverageAnnualReturnYear05 2.09%
10 Years rr_AverageAnnualReturnYear10 4.48%
Since Inception rr_AverageAnnualReturnSinceInception 6.97%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class A, C, S, I, T Shares | Russell 2000® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (4.18%)
5 Years rr_AverageAnnualReturnYear05 0.15%
10 Years rr_AverageAnnualReturnYear10 5.62%
Since Inception rr_AverageAnnualReturnSinceInception 8.96%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Venture Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Venture Fund seeks capital appreciation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 54% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 54.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing at least 50% of its equity assets in small-sized companies. The Fund may also invest in larger companies with strong growth potential or relatively well-known and large companies with potential for capital appreciation. Small-sized companies are defined by the portfolio managers as those companies whose market capitalization falls within the range of companies in the Russell 2000® Growth Index. Market capitalization is a commonly used measure of the size and value of a company. The market capitalizations within the index will vary, but as of September 30, 2011, they ranged from approximately $29 million to $3.7 billion. Companies whose capitalization or revenues fall outside these ranges after the Fund’s initial purchase continue to be considered small-sized.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Small-Sized Companies Risk. The Fund’s investments in securities issued by small-sized companies, which tend to be smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. Securities issued by small-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger companies.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter:  Second Quarter 2009  28.30%          Worst Quarter:  Fourth Quarter 2008  -28.61%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Venture Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.85%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 87
3 Years rr_ExpenseExampleYear03 271
5 Years rr_ExpenseExampleYear05 471
10 Years rr_ExpenseExampleYear10 1,049
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (27.24%)
2003 rr_AnnualReturn2003 55.75%
2004 rr_AnnualReturn2004 17.56%
2005 rr_AnnualReturn2005 1.55%
2006 rr_AnnualReturn2006 23.58%
2007 rr_AnnualReturn2007 16.36%
2008 rr_AnnualReturn2008 (51.43%)
2009 rr_AnnualReturn2009 54.50%
2010 rr_AnnualReturn2010 27.07%
2011 rr_AnnualReturn2011 2.20%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 28.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (28.61%)
Janus Venture Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.20%
5 Years rr_AverageAnnualReturnYear05 2.55%
10 Years rr_AverageAnnualReturnYear10 6.61%
Since Inception rr_AverageAnnualReturnSinceInception 11.54%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 1.09%
5 Years rr_AverageAnnualReturnYear05 1.57%
10 Years rr_AverageAnnualReturnYear10 5.85%
Since Inception rr_AverageAnnualReturnSinceInception 9.39%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.90%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 5.73%
Since Inception rr_AverageAnnualReturnSinceInception 9.34%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class D Shares | Russell 2000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.91%)
5 Years rr_AverageAnnualReturnYear05 2.09%
10 Years rr_AverageAnnualReturnYear10 4.48%
Since Inception rr_AverageAnnualReturnSinceInception 6.97%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Venture Fund | Class D Shares | Russell 2000® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 2000® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (4.18%)
5 Years rr_AverageAnnualReturnYear05 0.15%
10 Years rr_AverageAnnualReturnYear10 5.62%
Since Inception rr_AverageAnnualReturnSinceInception 8.96%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Twenty Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Twenty Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 56% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 56.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing primarily in a core group of 20-30 common stocks selected for their growth potential. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter:  Second Quarter 2009  19.94%          Worst Quarter:  Third Quarter 2008  -26.00%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Twenty Fund | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.82%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 84
3 Years rr_ExpenseExampleYear03 262
5 Years rr_ExpenseExampleYear05 455
10 Years rr_ExpenseExampleYear10 1,014
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (24.02%)
2003 rr_AnnualReturn2003 25.31%
2004 rr_AnnualReturn2004 23.89%
2005 rr_AnnualReturn2005 9.42%
2006 rr_AnnualReturn2006 12.30%
2007 rr_AnnualReturn2007 35.94%
2008 rr_AnnualReturn2008 (41.97%)
2009 rr_AnnualReturn2009 43.27%
2010 rr_AnnualReturn2010 7.07%
2011 rr_AnnualReturn2011 (8.04%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 19.94%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.00%)
Janus Twenty Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.04%)
5 Years rr_AverageAnnualReturnYear05 2.16%
10 Years rr_AverageAnnualReturnYear10 4.90%
Since Inception rr_AverageAnnualReturnSinceInception 11.22%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (10.16%)
5 Years rr_AverageAnnualReturnYear05 1.67%
10 Years rr_AverageAnnualReturnYear10 4.59%
Since Inception rr_AverageAnnualReturnSinceInception 9.66%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (2.41%)
5 Years rr_AverageAnnualReturnYear05 1.85%
10 Years rr_AverageAnnualReturnYear10 4.25%
Since Inception rr_AverageAnnualReturnSinceInception 9.33%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 10.15%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class D Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 9.56%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Twenty Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Twenty Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 56% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 56.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing primarily in a core group of 20-30 common stocks selected for their growth potential. The Fund may also invest in foreign equity and debt securities, which may include investments in emerging markets.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 19.94%          Worst Quarter: Third Quarter 2008 -26.00%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Twenty Fund | Class T Shares | Class T
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.94%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 96
3 Years rr_ExpenseExampleYear03 300
5 Years rr_ExpenseExampleYear05 520
10 Years rr_ExpenseExampleYear10 1,155
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (24.02%)
2003 rr_AnnualReturn2003 25.31%
2004 rr_AnnualReturn2004 23.89%
2005 rr_AnnualReturn2005 9.42%
2006 rr_AnnualReturn2006 12.30%
2007 rr_AnnualReturn2007 35.94%
2008 rr_AnnualReturn2008 (41.97%)
2009 rr_AnnualReturn2009 43.27%
2010 rr_AnnualReturn2010 6.97%
2011 rr_AnnualReturn2011 (8.19%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 19.94%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.00%)
Janus Twenty Fund | Class T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.19%)
5 Years rr_AverageAnnualReturnYear05 2.11%
10 Years rr_AverageAnnualReturnYear10 4.87%
Since Inception rr_AverageAnnualReturnSinceInception 11.21%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (10.30%)
5 Years rr_AverageAnnualReturnYear05 1.62%
10 Years rr_AverageAnnualReturnYear10 4.57%
Since Inception rr_AverageAnnualReturnSinceInception 9.65%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (2.53%)
5 Years rr_AverageAnnualReturnYear05 1.80%
10 Years rr_AverageAnnualReturnYear10 4.23%
Since Inception rr_AverageAnnualReturnSinceInception 9.32%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 10.15%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Twenty Fund | Class T Shares | Russell 1000® Growth Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Russell 1000® Growth Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.64%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 2.60%
Since Inception rr_AverageAnnualReturnSinceInception 9.56%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1985
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Market Neutral Fund (formerly named Janus Long/Short Fund)
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Market Neutral Fund seeks long-term capital appreciation independent of stock market direction.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 30 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 228% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 228.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund’s market neutral strategy attempts to create a portfolio that limits stock market risk and delivers absolute returns. Under normal circumstances, the Fund generally pursues its investment objective by taking both long and short positions in domestic and foreign equity securities, including those in emerging markets, and exchange-traded funds (“ETFs”) in an effort to insulate the Fund’s performance from general stock market movements. The Fund seeks a combination of long and short positions that may provide positive returns regardless of market direction, through a complete market cycle. The Fund will generally buy long securities that the portfolio manager believes will go up in price and will sell short ETFs and other equity securities the portfolio manager believes will go down in price. The Fund may also take long and short positions in derivative instruments that provide exposure to the equity markets, including swaps, options, futures, and other index-based instruments. The Fund’s investments may include holdings across different industries, sectors, and regions. The Fund normally invests in issuers from several different countries, including the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may also have significant exposure to emerging markets.

The allocation between long and short positions is a result of the portfolio manager’s strategic investment process. As a residual of the investment process, the Fund will generally hold a higher percentage of its assets in long positions than short positions (i.e., the Fund will be “net long”). Under normal circumstances, the Fund expects to be no more than 20% net long. The portfolio manager will actively manage the Fund’s net exposure between long and short positions and will determine that the Fund’s allocation be modified based on certain factors, including changes in market conditions.

In choosing long positions, the Fund’s portfolio manager looks at companies individually to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The Fund’s portfolio manager may seek long positions in companies with attractive dividends, return on invested capital, or with attractive price/free cash flow, which is the relationship between the price of a stock and the company’s available cash from operations, minus capital expenditures.

The Fund’s portfolio manager will generally target short positions in ETFs, either directly or through derivative instruments, such as swaps, which may provide similar exposure to a direct short position. The portfolio manager may deploy unique strategies when shorting ETFs and/or securities to minimize risk. For example, some investments may be held short to remove some of the market risk of a long position while accentuating the information advantage the portfolio manager believes he has in a long position in the portfolio. The Fund may invest in or short any type of ETF.

The Fund intends to also write (sell) covered call options on individual equity securities held long in an effort to generate income and to reduce the overall volatility of the Fund. A call option is “covered” when the Fund either holds the security subject to the option or an option to purchase the same security at an exercise price equal to or less than the exercise price of the covered call option. When the Fund writes a covered call option, the Fund makes an obligation to deliver the security at an agreed-upon strike price on or before a predetermined date in the future in return for a premium. The Fund may also engage in other types of options transactions in order to achieve its investment objective.

In addition to taking short positions in ETFs, the Fund’s portfolio manager may also take short positions in other equity securities. In general, a short position is one where the Fund has sold at the current market price a security that it does not own in anticipation of a decline in the market value of the security. To complete a short sale, the Fund must borrow the security to make delivery to the buyer. The Fund then is obligated to replace the borrowed security by purchasing the security at the market price at the time of replacement. The price at such time may be more or less than the price at which the security was sold by the Fund. Until the borrowed security is replaced, the Fund is required to pay to the lender amounts equal to any dividends or interest that accrue during the period of the loan. To borrow the security, the Fund also may be required to pay a premium to the lender, which would increase the cost of the security sold. The proceeds of the short sale will be retained by the broker to the extent necessary to meet margin requirements, until the short position is closed.

Until the Fund closes its short position or replaces the borrowed security, the Fund will designate liquid assets it owns (other than the short sale proceeds) as segregated assets in an amount equal to its obligation to purchase the securities sold short, as required under the Investment Company Act of 1940, as amended (the “1940 Act”). The amount segregated in this manner will be increased or decreased each business day equal to the change in market value of the Fund’s obligation to purchase the security sold short. If the lending broker requires the Fund to deposit collateral (in addition to the short sales proceeds that the broker holds during the period of the short sale), which may be as much as 50% of the value of the securities sold short, the amount of the additional collateral may be deducted in determining the amount of cash or liquid assets the Fund is required to segregate to cover the short sale obligation pursuant to the 1940 Act. The amount segregated must be unencumbered by any other obligation or claim other than the obligation that is being covered. The Fund believes that short sale obligations that are covered, either by an offsetting asset or right (acquiring the security sold short or having an option to purchase the security sold short at an exercise price that covers the obligation), or by the Fund’s segregated asset procedures (or a combination thereof), are not senior securities under the 1940 Act and are not subject to the Fund’s borrowing restrictions. This requirement to segregate assets limits the Fund’s leveraging of its investments and the related risk of losses from leveraging. The Fund also is required to pay the lender of the security any dividends or interest that accrues on a borrowed security during the period of the loan. Depending on the arrangements made with the broker or custodian, the Fund may or may not receive any payments (including interest) on collateral it has deposited with the broker.

The Fund may borrow money from banks to the extent permitted by the 1940 Act, including for investment purposes. Such borrowings may be on a secured or unsecured basis at fixed or variable rates of interest. The 1940 Act requires the Fund to maintain continuous asset coverage of not less than 300% with respect to all borrowings that are considered “senior securities” (generally borrowings other than for temporary or emergency purposes). This allows the Fund to borrow from banks up to 1/3 of its total assets (including the amount borrowed). If such asset coverage should decline to less than 300% due to market fluctuations or other reasons, the Fund may be required to dispose of some of its portfolio holdings within three days in order to reduce the Fund’s debt and restore the 300% asset coverage, even though it may be disadvantageous from an investment standpoint to dispose of assets at that time. The Fund’s short sales and related margin requirements may reduce the ability of the Fund to borrow money.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund invests primarily in common stocks, which tend to be more volatile than many other investment choices.

Long/Short Position Risk. The value of the Fund’s long portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the Fund’s portfolio manager is incorrect about his assessment of a company’s intrinsic worth. Further, regardless of how well individual companies or securities perform, the value of the Fund’s long portfolio could also decrease if there are deteriorating economic or market conditions, including, but not limited to, a general decline in prices on the stock markets, a general decline in real estate markets, a decline in commodities prices, or if the market favors different types of securities than the types of securities in which the Fund invests. Conversely, the value of the Fund’s short positions may result in a loss (which may be unlimited) if the value of an individual company or security, or multiple companies or securities, in the portfolio increases or if the stock market goes up, regardless of how well the businesses of individual companies or securities in the portfolio perform. If the value of the Fund’s portfolio decreases, the Fund’s net asset value will also decrease, which means if you sell your shares in the Fund you may lose money.

Short Sales Risk. Short sales are speculative transactions and involve special risks, including a greater reliance on the portfolio manager’s ability to accurately anticipate the future value of a security. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. The Fund’s losses are potentially unlimited in a short sale transaction. The use of short sales may also cause the Fund to have higher expenses than those of other funds. In addition, due to the investment process of long and short positions, the Fund may be subject to additional transaction costs that may lower the Fund’s returns. The Fund’s use of short sales may also have a leveraging effect on the Fund’s portfolio.

Market Neutral Style Risk. The Fund’s market neutral strategy may cause the Fund to underperform compared to global equity markets or other mutual funds that do not utilize a market neutral strategy. For example, in rising global equity markets, the Fund’s short positions may significantly impact the Fund’s overall performance and cause the Fund to underperform or sustain losses, especially in sharply rising markets. As such, the Fund’s combination of long and short positions may result in performance that is significantly different from global equity markets. Periodic underperformance is to be expected and is a result of the Fund’s overall hedging techniques employed for the market neutral strategy. Additionally, there is a risk that the portfolio manager will be unable to construct a portfolio that limits the Fund’s exposure to market movements, and as a result, the Fund’s performance may reflect general market movements.

Counterparty Risk. Certain derivative and “over-the-counter” instruments, such as swaps and forwards, are subject to the risk that the other party to a contract will not fulfill its contractual obligations.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 2.5% of the Fund’s investments in long positions were in emerging markets.

Exchange-Traded Funds Risk. The Fund may invest in or short ETFs which are typically open-end investment companies that are traded on a national securities exchange. ETFs typically incur fees, such as investment advisory and other operating expenses that are separate from those of the Fund, which will be indirectly paid by the Fund. As a result, the cost of investing in the Fund may be higher than the cost of investing directly in ETFs and may be higher than other mutual funds that invest directly in stocks and bonds. Further, the price movement of an ETF may fluctuate against the underlying index it tracks and may result in a loss. Because the value of ETF shares depends on the demand in the market, the Fund may not be able to purchase or sell an ETF at the most optimal time, which could adversely affect the Fund’s performance.

The ETFs in which the Fund invests are subject to specific risks, depending on the investment strategy of the ETF. In turn, the Fund will be subject to substantially the same risks as those associated with direct exposure to the securities held by the ETF. Because the Fund may invest in a broad range of ETFs, such risks may include, but are not limited to, leverage risk, foreign exposure risk, and commodities risk. Similarly, short sales of ETF shares are speculative transactions and are subject to other specific risks. In addition, if the Fund sells short shares in ETFs that are financially leveraged, such short sales may be expected to exhibit enhanced volatility in market price as compared to short sales of shares of similar ETFs without a leveraged capital structure, which may negatively affect the Fund’s returns.

Options Writing Strategy Risk. During periods in which the equity markets are generally unchanged or falling, a portfolio such as that held by the Fund which utilizes a covered call option writing strategy may outperform the same portfolio without a covered call option writing strategy because of the additional premiums received from writing covered call options. Similarly, in a modestly rising market, the Fund may also outperform the same portfolio without a covered call option writing strategy. However, in sharply rising markets, the Fund is expected to underperform the same portfolio that does not employ a covered call option writing strategy. This underperformance in a sharply rising market could be significant. The Fund’s covered call option writing strategy may not fully protect it against declines in the value of the equity markets. The successful use of an option writing strategy depends in part on the ability of the portfolio manager to anticipate price fluctuations and the degree of correlation between the options and securities markets. Market volatility may also have a significant impact on the efficient execution and pricing of the option writing strategy. There are significant differences between the securities and options markets, which could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives.

Borrowing Risk. Because the Fund may borrow money from banks for investment purposes, commonly referred to as “leveraging,” the Fund’s exposure to fluctuations in the prices of these securities is increased in relation to the Fund’s capital. The Fund’s borrowing activities will exaggerate any increase or decrease in the net asset value of the Fund. In addition, the interest which the Fund must pay on borrowed money, together with any additional fees to maintain a line of credit or any minimum average balances, are additional costs which will reduce or eliminate any net investment profits. Unless profits on assets acquired with borrowed funds exceed the costs of borrowing, the use of borrowing will diminish the investment performance of the Fund compared with what it would have been without borrowing.

Leverage Risk. Leverage occurs when the Fund increases its assets available for investment through borrowings or similar transactions.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Long/Short Fund (“JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares prior to the reorganization, calculated using the fees and expenses of each respective share class of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class T Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares prior to the reorganization, calculated using the fees and expenses of Class I Shares, without the effect of any fee and expense limitations or waivers.

If Class T Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class I Shares, Class A Shares, Class C Shares, Class S Shares, Class R Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class I Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter:  Third Quarter 2009  9.28%          Worst Quarter:  First Quarter 2009  -13.38%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

Effective September 30, 2011, the Fund changed its primary benchmark index from the S&P 500® Index to the Citigroup 3-Month U.S. Treasury Bill Index. The Citigroup 3-Month U.S. Treasury Bill Index is an index that tracks the performance of short-term U.S. Government debt securities. In addition, the Fund changed its secondary benchmark index from the LIBOR to the Morgan Stanley Capital International (“MSCI”) All Country World IndexSM. The MSCI All Country World IndexSM is an unmanaged, free float-adjusted, market capitalization weighted index composed of stocks of companies located in countries throughout the world. It is designed to measure equity market performance in global developed and emerging markets. The index includes reinvestment of dividends, net of foreign withholding taxes. Janus Capital believes that these changes provide a more appropriate representation of the Fund’s investment strategy that includes an increased focus on global investments, including emerging markets.

After-tax returns are calculated using distributions for the Fund’s Class I Shares for periods following July 6, 2009; and for the JAD predecessor fund’s Class I Shares for periods prior to July 6, 2009. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.53%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.53%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.03% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.03% [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 4.00% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 957
3 Years rr_ExpenseExampleYear03 1,731
5 Years rr_ExpenseExampleYear05 2,521
10 Years rr_ExpenseExampleYear10 4,563
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 957
3 Years rr_ExpenseExampleNoRedemptionYear03 1,731
5 Years rr_ExpenseExampleNoRedemptionYear05 2,521
10 Years rr_ExpenseExampleNoRedemptionYear10 4,563
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 2.40%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.40%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.65% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 4.65% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 566
3 Years rr_ExpenseExampleYear03 1,402
5 Years rr_ExpenseExampleYear05 2,345
10 Years rr_ExpenseExampleYear10 4,732
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 466
3 Years rr_ExpenseExampleNoRedemptionYear03 1,402
5 Years rr_ExpenseExampleNoRedemptionYear05 2,345
10 Years rr_ExpenseExampleNoRedemptionYear10 4,732
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.57%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.57%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.07% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 4.07% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 409
3 Years rr_ExpenseExampleYear03 1,238
5 Years rr_ExpenseExampleYear05 2,083
10 Years rr_ExpenseExampleYear10 4,264
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 409
3 Years rr_ExpenseExampleNoRedemptionYear03 1,238
5 Years rr_ExpenseExampleNoRedemptionYear05 2,083
10 Years rr_ExpenseExampleNoRedemptionYear10 4,264
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.49%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.74% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 3.74% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 376
3 Years rr_ExpenseExampleYear03 1,143
5 Years rr_ExpenseExampleYear05 1,930
10 Years rr_ExpenseExampleYear10 3,984
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 376
3 Years rr_ExpenseExampleNoRedemptionYear03 1,143
5 Years rr_ExpenseExampleNoRedemptionYear05 1,930
10 Years rr_ExpenseExampleNoRedemptionYear10 3,984
Annual Total Returns rr_BarChartTableAbstract  
2007 rr_AnnualReturn2007 16.56%
2008 rr_AnnualReturn2008 (23.68%)
2009 rr_AnnualReturn2009 4.56%
2010 rr_AnnualReturn2010 2.78%
2011 rr_AnnualReturn2011 (3.83%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 9.28%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2009
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (13.38%)
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 2.57%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.57%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.32% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 4.32% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 433
3 Years rr_ExpenseExampleYear03 1,309
5 Years rr_ExpenseExampleYear05 2,197
10 Years rr_ExpenseExampleYear10 4,470
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 433
3 Years rr_ExpenseExampleNoRedemptionYear03 1,309
5 Years rr_ExpenseExampleNoRedemptionYear05 2,197
10 Years rr_ExpenseExampleNoRedemptionYear10 4,470
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 1.25%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.59%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 2.00%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.59%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.84% [7]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets none [7]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 3.84% [7]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 386
3 Years rr_ExpenseExampleYear03 1,172
5 Years rr_ExpenseExampleYear05 1,976
10 Years rr_ExpenseExampleYear10 4,070
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 386
3 Years rr_ExpenseExampleNoRedemptionYear03 1,172
5 Years rr_ExpenseExampleNoRedemptionYear05 1,976
10 Years rr_ExpenseExampleNoRedemptionYear10 4,070
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (9.68%)
5 Years rr_AverageAnnualReturnYear05 (3.12%)
Since Inception rr_AverageAnnualReturnSinceInception (0.82%)
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (5.49%)
5 Years rr_AverageAnnualReturnYear05 (2.56%)
Since Inception rr_AverageAnnualReturnSinceInception (0.35%)
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.16%)
5 Years rr_AverageAnnualReturnYear05 (2.02%)
Since Inception rr_AverageAnnualReturnSinceInception 0.19%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (3.83%)
5 Years rr_AverageAnnualReturnYear05 (1.67%)
Since Inception rr_AverageAnnualReturnSinceInception 0.57%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.39%)
5 Years rr_AverageAnnualReturnYear05 (3.37%)
Since Inception rr_AverageAnnualReturnSinceInception (1.11%)
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (3.96%)
5 Years rr_AverageAnnualReturnYear05 (1.69%)
Since Inception rr_AverageAnnualReturnSinceInception 0.55%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (6.45%)
5 Years rr_AverageAnnualReturnYear05 (2.31%)
Since Inception rr_AverageAnnualReturnSinceInception (0.07%)
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (1.80%)
5 Years rr_AverageAnnualReturnYear05 (1.67%)
Since Inception rr_AverageAnnualReturnSinceInception 0.22%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
Since Inception rr_AverageAnnualReturnSinceInception 1.97%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
Since Inception rr_AverageAnnualReturnSinceInception 0.61%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | Citigroup 3-Month U.S. Treasury Bill Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Citigroup 3-Month U.S. Treasury Bill Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 0.08%
5 Years rr_AverageAnnualReturnYear05 1.36%
Since Inception rr_AverageAnnualReturnSinceInception 1.65%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Market Neutral Fund | Class A, C, S, I, R, T Shares | LIBOR
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel LIBOR
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 0.35%
5 Years rr_AverageAnnualReturnYear05 1.86%
Since Inception rr_AverageAnnualReturnSinceInception 2.12%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2006
Janus Global Real Estate Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Real Estate Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Real Estate Fund seeks total return through a combination of capital appreciation and current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 31 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 68% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 68.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets plus the amount of any borrowings for investment purposes, in equity and debt securities of real estate-related companies. Such companies may include those in the real estate industry or real estate-related industries. These securities may include common stocks, preferred stocks, and other equity securities, including, but not limited to, real estate investment trusts (“REITs”) and similar REIT-like entities.

As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries. The Fund’s investment in companies engaged in businesses outside the real estate industry which possess significant real estate holdings will be deemed to be in the real estate industry for purposes of the Fund’s investment objective and its policy on industry concentration.

Real estate-related industries are comprised of companies that, in the opinion of the portfolio manager, at the time of investment, generally (i) derive at least 50% of their revenue from ownership, construction, extraction, financing, management, operation, sales or development of real estate, or from businesses which have a clear relationship to these activities; (ii) have at least 50% of their assets in real estate; or (iii) have more than 50% of their net asset value accounted for by real estate. A REIT is a company dedicated to owning, and usually operating, income producing real estate, or to financing real estate. REITs pool investors’ funds for investment primarily in income producing real estate or real estate-related loans or interests. Under the Internal Revenue Code of 1986, as amended (the “Code”), a REIT is not taxed on income it distributes to its shareholders if it complies with several requirements relating to its organization, ownership, assets and income, and a requirement that it generally distribute to its shareholders at least 90% of its taxable income (other than net capital gains) for each taxable year.

The Fund also invests in non-U.S. real estate and real estate-related companies. The Fund expects under normal market conditions to maintain investments in issuers from several different developed countries, including the United States. Under unusual circumstances, the Fund may invest all of its assets in a single country. The Fund may invest in emerging markets but will normally limit such investments to 15% of its net assets, measured at the time of purchase.

In selecting the investments for the Fund, the portfolio manager seeks to identify companies that have, in the opinion of the portfolio manager, good management, strong balance sheets, above average investment growth in “funds from operations,” and that trade at a discount to their assets’ underlying value. In the case of REITs, “funds from operations” generally means a REIT’s net income excluding gains or losses from debt restructuring and sales of property plus depreciation of real property.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors interested in investments focused in the real estate industry or real estate-related industries, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 9.9% of the Fund’s investments were in emerging markets.

Real Estate Risk. An investment in the Fund may be subject to many of the same risks as a direct investment in real estate. The value of securities of issuers in the real estate and real estate-related industries, including REITs, is sensitive to changes in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, supply and demand, and the management skill and creditworthiness of the issuer. These factors may impact the Fund’s investments in foreign real estate markets differently than U.S. real estate markets.

Concentration Risk. Since the Fund concentrates its assets in the real estate or real estate-related industry, an investment in the Fund will be closely linked to performance of the real estate markets. As a result, the Fund may be subject to greater risks and its net asset value may fluctuate more than a fund that does not concentrate its investments.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class I Shares, Class A Shares, Class C Shares, and Class S Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Global Real Estate Fund (“JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class I Shares, Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares, Class A Shares, Class C Shares, and Class S Shares prior to the reorganization, calculated using the fees and expenses of each respective share class of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class T Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares prior to the reorganization, calculated using the fees and expenses of Class T Shares, without the effect of any fee and expense limitations or waivers.

If Class T Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class I Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter:  Second Quarter 2009  35.29%          Worst Quarter:  Fourth Quarter 2008  -27.24%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class I Shares for periods following July 6, 2009; and for the JAD predecessor fund’s Class I Shares for periods prior to July 6, 2009. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.80%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.44%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.49%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 718
3 Years rr_ExpenseExampleYear03 1,019
5 Years rr_ExpenseExampleYear05 1,341
10 Years rr_ExpenseExampleYear10 2,252
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 718
3 Years rr_ExpenseExampleNoRedemptionYear03 1,019
5 Years rr_ExpenseExampleNoRedemptionYear05 1,341
10 Years rr_ExpenseExampleNoRedemptionYear10 2,252
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.80%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.39%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.19%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 322
3 Years rr_ExpenseExampleYear03 685
5 Years rr_ExpenseExampleYear05 1,175
10 Years rr_ExpenseExampleYear10 2,524
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 222
3 Years rr_ExpenseExampleNoRedemptionYear03 685
5 Years rr_ExpenseExampleNoRedemptionYear05 1,175
10 Years rr_ExpenseExampleNoRedemptionYear10 2,524
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.80%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.58%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.63%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 166
3 Years rr_ExpenseExampleYear03 514
5 Years rr_ExpenseExampleYear05 887
10 Years rr_ExpenseExampleYear10 1,933
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 166
3 Years rr_ExpenseExampleNoRedemptionYear03 514
5 Years rr_ExpenseExampleNoRedemptionYear05 887
10 Years rr_ExpenseExampleNoRedemptionYear10 1,933
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.80%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.41%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.21%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 123
3 Years rr_ExpenseExampleYear03 384
5 Years rr_ExpenseExampleYear05 665
10 Years rr_ExpenseExampleYear10 1,466
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 123
3 Years rr_ExpenseExampleNoRedemptionYear03 384
5 Years rr_ExpenseExampleNoRedemptionYear05 665
10 Years rr_ExpenseExampleNoRedemptionYear10 1,466
Annual Total Returns rr_BarChartTableAbstract  
2008 rr_AnnualReturn2008 (40.57%)
2009 rr_AnnualReturn2009 48.89%
2010 rr_AnnualReturn2010 21.13%
2011 rr_AnnualReturn2011 (13.54%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 35.29%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.24%)
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.80%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.55%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.35%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 137
3 Years rr_ExpenseExampleYear03 428
5 Years rr_ExpenseExampleYear05 739
10 Years rr_ExpenseExampleYear10 1,624
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 137
3 Years rr_ExpenseExampleNoRedemptionYear03 428
5 Years rr_ExpenseExampleNoRedemptionYear05 739
10 Years rr_ExpenseExampleNoRedemptionYear10 1,624
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (18.70%)
Since Inception rr_AverageAnnualReturnSinceInception (4.29%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (15.30%)
Since Inception rr_AverageAnnualReturnSinceInception (3.47%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.96%)
Since Inception rr_AverageAnnualReturnSinceInception (3.05%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.54%)
Since Inception rr_AverageAnnualReturnSinceInception (2.67%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.48%)
Since Inception rr_AverageAnnualReturnSinceInception (4.03%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.78%)
Since Inception rr_AverageAnnualReturnSinceInception (3.30%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.36%)
Since Inception rr_AverageAnnualReturnSinceInception (2.53%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | FTSE EPRA/NAREIT Global Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Global Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (8.14%)
Since Inception rr_AverageAnnualReturnSinceInception (5.91%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class A, C, S, I, T Shares | FTSE EPRA/NAREIT Developed Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Developed Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.82%)
Since Inception rr_AverageAnnualReturnSinceInception (5.37%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Real Estate Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Real Estate Fund seeks total return through a combination of capital appreciation and current income.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 68% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 68.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets plus the amount of any borrowings for investment purposes, in equity and debt securities of real estate-related companies. Such companies may include those in the real estate industry or real estate-related industries. These securities may include common stocks, preferred stocks, and other equity securities, including, but not limited to, real estate investment trusts (“REITs”) and similar REIT-like entities.

As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries. The Fund’s investment in companies engaged in businesses outside the real estate industry which possess significant real estate holdings will be deemed to be in the real estate industry for purposes of the Fund’s investment objective and its policy on industry concentration.

Real estate-related industries are comprised of companies that, in the opinion of the portfolio manager, at the time of investment, generally (i) derive at least 50% of their revenue from ownership, construction, extraction, financing, management, operation, sales or development of real estate, or from businesses which have a clear relationship to these activities; (ii) have at least 50% of their assets in real estate; or (iii) have more than 50% of their net asset value accounted for by real estate. A REIT is a company dedicated to owning, and usually operating, income producing real estate, or to financing real estate. REITs pool investors’ funds for investment primarily in income producing real estate or real estate-related loans or interests. Under the Internal Revenue Code of 1986, as amended (the “Code”), a REIT is not taxed on income it distributes to its shareholders if it complies with several requirements relating to its organization, ownership, assets and income, and a requirement that it generally distribute to its shareholders at least 90% of its taxable income (other than net capital gains) for each taxable year.

The Fund also invests in non-U.S. real estate and real estate-related companies. The Fund expects under normal market conditions to maintain investments in issuers from several different developed countries, including the United States. Under unusual circumstances, the Fund may invest all of its assets in a single country. The Fund may invest in emerging markets but will normally limit such investments to 15% of its net assets, measured at the time of purchase.

In selecting the investments for the Fund, the portfolio manager seeks to identify companies that have, in the opinion of the portfolio manager, good management, strong balance sheets, above average investment growth in “funds from operations,” and that trade at a discount to their assets’ underlying value. In the case of REITs, “funds from operations” generally means a REIT’s net income excluding gains or losses from debt restructuring and sales of property plus depreciation of real property.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors interested in investments focused in the real estate industry or real estate-related industries, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 9.9% of the Fund’s investments were in emerging markets.

Real Estate Risk. An investment in the Fund may be subject to many of the same risks as a direct investment in real estate. The value of securities of issuers in the real estate and real estate-related industries, including REITs, is sensitive to changes in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, supply and demand, and the management skill and creditworthiness of the issuer. These factors may impact the Fund’s investments in foreign real estate markets differently than U.S. real estate markets.

Concentration Risk. Since the Fund concentrates its assets in the real estate or real estate-related industry, an investment in the Fund will be closely linked to performance of the real estate markets. As a result, the Fund may be subject to greater risks and its net asset value may fluctuate more than a fund that does not concentrate its investments.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Fixed-Income Securities Risk. The Fund may hold debt and other fixed-income securities to generate income. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that their value will generally decline as prevailing interest rates rise, which may cause the Fund’s net asset value to likewise decrease. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, and liquidity risk.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s Class I Shares calculated using the fees and expenses of Class D Shares, without the effect of any fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 33.35%          Worst Quarter: Fourth Quarter 2008 -27.54%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class I Shares for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Global Real Estate Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.80%
Other Expenses rr_OtherExpensesOverAssets 0.55%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.35%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 137
3 Years rr_ExpenseExampleYear03 428
5 Years rr_ExpenseExampleYear05 739
10 Years rr_ExpenseExampleYear10 1,624
Annual Total Returns rr_BarChartTableAbstract  
2008 rr_AnnualReturn2008 (42.95%)
2009 rr_AnnualReturn2009 42.63%
2010 rr_AnnualReturn2010 20.46%
2011 rr_AnnualReturn2011 (13.53%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 33.35%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.54%)
Janus Global Real Estate Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.53%)
Since Inception rr_AverageAnnualReturnSinceInception (4.87%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.75%)
Since Inception rr_AverageAnnualReturnSinceInception (5.46%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.38%)
Since Inception rr_AverageAnnualReturnSinceInception (4.34%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class D Shares | FTSE EPRA/NAREIT Global Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Global Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (8.14%)
Since Inception rr_AverageAnnualReturnSinceInception (5.91%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Global Real Estate Fund | Class D Shares | FTSE EPRA/NAREIT Developed Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Developed Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.82%)
Since Inception rr_AverageAnnualReturnSinceInception (5.37%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2007
Janus Asia Equity Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Asia Equity Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Asia Equity Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 12% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 12.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities of Asian issuers (excluding Japanese issuers). An Asian issuer is generally considered to be any company that (i) is incorporated or has its principal business activities in an Asian country; (ii) is primarily listed on the trading market of an Asian country; or (iii) derives 50% or more of its revenue from, or has 50% or more of its assets in, one or more Asian countries. The Fund considers “Asian countries” to include, but not be limited to, Hong Kong, China, South Korea, Taiwan, Singapore, Malaysia, Thailand, Indonesia, Philippines, India, Vietnam, Pakistan, Russia, and Sri Lanka. Some of these countries may represent developing or emerging markets.

The Fund generally invests in equity securities, which consist primarily of common stocks, preferred stocks, depositary receipts, and convertible securities, but may also include other types of instruments, such as equity-linked securities and real estate investment trusts issued by Asian real estate companies. The Fund may invest in companies of any market capitalization. While the Fund intends to diversify its investments across a number of different countries, including emerging market countries, it may, under unusual circumstances, invest all or a significant portion of its assets in a single Asian country. To a more limited degree, the Fund may also invest in U.S. and foreign debt securities. Due to the nature of the securities in which the Fund invests, it may have relatively high portfolio turnover compared to other funds.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio manager will also analyze each company from a macro perspective taking into consideration any important themes or issues that may impact the investment environment in certain regions or sectors and to estimate regional market risks.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. For purposes of meeting the 80% investment policy, the Fund may include derivatives that have characteristics similar to the Fund’s direct investments. The Fund has invested in and may continue to invest in derivatives, such as swaps, to gain access to foreign markets, in particular where direct investment may be restricted or unavailable. The Fund may also invest in derivative instruments (by taking long and/or short positions) for other purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an Asian equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 59.4% of the Fund’s investments were in emerging markets.

Geographic Concentration Risk. Because the Fund intends to focus its investments in a particular geographic region, the Fund’s performance is expected to be closely tied to various factors such as social, financial, economic, and political conditions within that region or country. Specifically, the Fund’s investments in Asian issuers increase the Fund’s exposure to the risks associated with volatile securities markets, adverse exchange rates, social, political and regulatory developments, and economic environmental events (such as natural disasters) which may be particular to Asian countries. Events that negatively affect the fiscal stability of Asian countries may cause the value of the Fund’s shares to decrease, in some cases significantly. As a result, the Fund is likely to be more volatile than more geographically diverse funds. In addition, many of the economies of the Asian countries in which the Fund invests are interdependent, which may cause them to experience the impact of such events at the same time or may increase the possibility that conditions in one country or region might adversely impact the issuers of securities in a different country or region.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The Fund does not have a full calendar year of operations. Performance information for certain periods is included in the Fund’s first annual and/or semiannual report.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess The Fund does not have a full calendar year of operations.
Janus Asia Equity Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.92%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.73% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.90% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.32% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.58% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 945
3 Years rr_ExpenseExampleYear03 1,696
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 945
3 Years rr_ExpenseExampleNoRedemptionYear03 1,696
Janus Asia Equity Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.92%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 2.75% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.67% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.34% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 2.33% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 568
3 Years rr_ExpenseExampleYear03 1,408
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 468
3 Years rr_ExpenseExampleNoRedemptionYear03 1,408
Janus Asia Equity Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.92%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.87% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.04% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.21% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.83% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 406
3 Years rr_ExpenseExampleYear03 1,230
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 406
3 Years rr_ExpenseExampleNoRedemptionYear03 1,230
Janus Asia Equity Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.92%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.64% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.56% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.23% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.33% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 359
3 Years rr_ExpenseExampleYear03 1,091
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 359
3 Years rr_ExpenseExampleNoRedemptionYear03 1,091
Janus Asia Equity Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.92%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.87% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.79% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.21% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.58% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 381
3 Years rr_ExpenseExampleYear03 1,158
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 381
3 Years rr_ExpenseExampleNoRedemptionYear03 1,158
Janus Asia Equity Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Asia Equity Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Asia Equity Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 12% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 12.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities of Asian issuers (excluding Japanese issuers). An Asian issuer is generally considered to be any company that (i) is incorporated or has its principal business activities in an Asian country; (ii) is primarily listed on the trading market of an Asian country; or (iii) derives 50% or more of its revenue from, or has 50% or more of its assets in, one or more Asian countries. The Fund considers “Asian countries” to include, but not be limited to, Hong Kong, China, South Korea, Taiwan, Singapore, Malaysia, Thailand, Indonesia, Philippines, India, Vietnam, Pakistan, Russia, and Sri Lanka. Some of these countries may represent developing or emerging markets.

The Fund generally invests in equity securities, which consist primarily of common stocks, preferred stocks, depositary receipts, and convertible securities, but may also include other types of instruments, such as equity-linked securities and real estate investment trusts issued by Asian real estate companies. The Fund may invest in companies of any market capitalization. While the Fund intends to diversify its investments across a number of different countries, including emerging market countries, it may, under unusual circumstances, invest all or a significant portion of its assets in a single Asian country. To a more limited degree, the Fund may also invest in U.S. and foreign debt securities. Due to the nature of the securities in which the Fund invests, it may have relatively high portfolio turnover compared to other funds.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio manager will also analyze each company from a macro perspective taking into consideration any important themes or issues that may impact the investment environment in certain regions or sectors and to estimate regional market risks.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. For purposes of meeting the 80% investment policy, the Fund may include derivatives that have characteristics similar to the Fund’s direct investments. The Fund has invested in and may continue to invest in derivatives, such as swaps, to gain access to foreign markets, in particular where direct investment may be restricted or unavailable. The Fund may also invest in derivative instruments (by taking long and/or short positions) for other purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an Asian equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 59.4% of the Fund’s investments were in emerging markets.

Geographic Concentration Risk. Because the Fund intends to focus its investments in a particular geographic region, the Fund’s performance is expected to be closely tied to various factors such as social, financial, economic, and political conditions within that region or country. Specifically, the Fund’s investments in Asian issuers increase the Fund’s exposure to the risks associated with volatile securities markets, adverse exchange rates, social, political and regulatory developments, and economic environmental events (such as natural disasters) which may be particular to Asian countries. Events that negatively affect the fiscal stability of Asian countries may cause the value of the Fund’s shares to decrease, in some cases significantly. As a result, the Fund is likely to be more volatile than more geographically diverse funds. In addition, many of the economies of the Asian countries in which the Fund invests are interdependent, which may cause them to experience the impact of such events at the same time or may increase the possibility that conditions in one country or region might adversely impact the issuers of securities in a different country or region.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The Fund does not have a full calendar year of operations. Performance information for certain periods is included in the Fund’s first annual and/or semiannual report.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess The Fund does not have a full calendar year of operations.
Janus Asia Equity Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.92%
Other Expenses rr_OtherExpensesOverAssets 2.99% [8]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.91% [10]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.38% [10]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.53% [10]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 393
3 Years rr_ExpenseExampleYear03 1,192
Janus Emerging Markets Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Emerging Markets Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Emerging Markets Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 211% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 211.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of issuers in emerging market countries. The Fund normally invests in securities of issuers that (i) are primarily listed on the trading market of an emerging market country; (ii) are incorporated or have their principal business activities in an emerging market country; or (iii) derive 50% or more of their revenues from, or have 50% or more of their assets in, an emerging market country. An emerging market country is any country that has been determined by an international organization, such as the World Bank, to have a low to middle income economy and/or any country that is not included in the Morgan Stanley Capital International World IndexSM, which measures the equity market performance of developed markets. The Fund generally invests in equity securities, which consist primarily of common stocks, preferred stocks and convertible securities, but may also invest in other types of instruments, such as equity-linked securities and exchange-traded funds. The Fund may invest in companies of any market capitalization. Due to the nature of the securities in which the Fund invests, it may have relatively high portfolio turnover compared to other funds.

Although the Fund intends to invest substantially all of its assets in several issuers located in emerging market countries, it may invest up to 20% of its net assets in securities of issuers located in the U.S. or other developed market issuers, and it may, under unusual circumstances, invest all or a significant portion of its assets in a single emerging market country. The Fund may also invest in domestic and foreign debt securities.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. For purposes of meeting the 80% investment policy, the Fund may include derivatives that have characteristics similar to the Fund’s direct investments. The Fund has invested in and may continue to invest in derivatives, such as swaps, to gain access to foreign markets, in particular where direct investment may be restricted or unavailable. The Fund may also invest in derivative instruments (by taking long and/or short positions) for other purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, particularly emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Exchange-Traded Funds Risk. The Fund may purchase shares of exchange-traded funds (“ETFs”) to gain exposure to a particular portion of the market. ETFs are pooled investment vehicles, which may be managed or unmanaged, that generally seek to track the performance of a specific index. ETFs are traded on an exchange at market prices that may vary from the net asset value of their underlying investments. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses. ETFs have certain inherent risks generally associated with investments in a portfolio of common stocks, including the risk that the general level of stock prices may decline, thereby adversely affecting the value of each unit of the ETF. ETFs also involve the risk that an active trading market for an ETF’s shares may not develop or be maintained.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. The bar chart depicts the Fund’s performance during the period indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the Fund’s performance during the period indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class I Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Fourth Quarter 2011 3.47%          Worst Quarter: Third Quarter 2011 -24.70%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.

Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.92%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.22% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.60% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.62% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 974
3 Years rr_ExpenseExampleYear03 1,782
5 Years rr_ExpenseExampleYear05 2,603
10 Years rr_ExpenseExampleYear10 4,711
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 974
3 Years rr_ExpenseExampleNoRedemptionYear03 1,782
5 Years rr_ExpenseExampleNoRedemptionYear05 2,603
10 Years rr_ExpenseExampleNoRedemptionYear10 4,711
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 3.10%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 5.15% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.78% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 2.37% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 615
3 Years rr_ExpenseExampleYear03 1,542
5 Years rr_ExpenseExampleYear05 2,565
10 Years rr_ExpenseExampleYear10 5,112
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 515
3 Years rr_ExpenseExampleNoRedemptionYear03 1,542
5 Years rr_ExpenseExampleNoRedemptionYear05 2,565
10 Years rr_ExpenseExampleNoRedemptionYear10 5,112
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 3.37%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.67% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.80% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.87% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 468
3 Years rr_ExpenseExampleYear03 1,408
5 Years rr_ExpenseExampleYear05 2,354
10 Years rr_ExpenseExampleYear10 4,748
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 468
3 Years rr_ExpenseExampleNoRedemptionYear03 1,408
5 Years rr_ExpenseExampleNoRedemptionYear05 2,354
10 Years rr_ExpenseExampleNoRedemptionYear10 4,748
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.88%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.93% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.56% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.37% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 395
3 Years rr_ExpenseExampleYear03 1,198
5 Years rr_ExpenseExampleYear05 2,018
10 Years rr_ExpenseExampleYear10 4,147
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 395
3 Years rr_ExpenseExampleNoRedemptionYear03 1,198
5 Years rr_ExpenseExampleNoRedemptionYear05 2,018
10 Years rr_ExpenseExampleNoRedemptionYear10 4,147
Annual Total Returns rr_BarChartTableAbstract  
2011 rr_AnnualReturn2011 (24.02%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.47%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.70%)
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 1.00%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 3.09%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.14% [9]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.52% [9]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.62% [9]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 416
3 Years rr_ExpenseExampleYear03 1,258
5 Years rr_ExpenseExampleYear05 2,115
10 Years rr_ExpenseExampleYear10 4,322
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 416
3 Years rr_ExpenseExampleNoRedemptionYear03 1,258
5 Years rr_ExpenseExampleNoRedemptionYear05 2,115
10 Years rr_ExpenseExampleNoRedemptionYear10 4,322
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (28.41%)
Since Inception rr_AverageAnnualReturnSinceInception (27.55%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (25.06%)
Since Inception rr_AverageAnnualReturnSinceInception (23.46%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (24.02%)
Since Inception rr_AverageAnnualReturnSinceInception (23.17%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (24.02%)
Since Inception rr_AverageAnnualReturnSinceInception (23.17%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (23.92%)
Since Inception rr_AverageAnnualReturnSinceInception (23.07%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (24.05%)
Since Inception rr_AverageAnnualReturnSinceInception (23.20%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (15.41%)
Since Inception rr_AverageAnnualReturnSinceInception (19.62%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International Emerging Markets Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International Emerging Markets IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (18.42%)
Since Inception rr_AverageAnnualReturnSinceInception (16.45%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Emerging Markets Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Emerging Markets Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 211% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 211.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of issuers in emerging market countries. The Fund normally invests in securities of issuers that (i) are primarily listed on the trading market of an emerging market country; (ii) are incorporated or have their principal business activities in an emerging market country; or (iii) derive 50% or more of their revenues from, or have 50% or more of their assets in, an emerging market country. An emerging market country is any country that has been determined by an international organization, such as the World Bank, to have a low to middle income economy and/or any country that is not included in the Morgan Stanley Capital International World IndexSM, which measures the equity market performance of developed markets. The Fund generally invests in equity securities, which consist primarily of common stocks, preferred stocks and convertible securities, but may also invest in other types of instruments, such as equity-linked securities and exchange-traded funds. The Fund may invest in companies of any market capitalization. Due to the nature of the securities in which the Fund invests, it may have relatively high portfolio turnover compared to other funds.

Although the Fund intends to invest substantially all of its assets in several issuers located in emerging market countries, it may invest up to 20% of its net assets in securities of issuers located in the U.S. or other developed market issuers, and it may, under unusual circumstances, invest all or a significant portion of its assets in a single emerging market country. The Fund may also invest in domestic and foreign debt securities.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. For purposes of meeting the 80% investment policy, the Fund may include derivatives that have characteristics similar to the Fund’s direct investments. The Fund has invested in and may continue to invest in derivatives, such as swaps, to gain access to foreign markets, in particular where direct investment may be restricted or unavailable. The Fund may also invest in derivative instruments (by taking long and/or short positions) for other purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, particularly emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Exchange-Traded Funds Risk. The Fund may purchase shares of exchange-traded funds (“ETFs”) to gain exposure to a particular portion of the market. ETFs are pooled investment vehicles, which may be managed or unmanaged, that generally seek to track the performance of a specific index. ETFs are traded on an exchange at market prices that may vary from the net asset value of their underlying investments. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses. ETFs have certain inherent risks generally associated with investments in a portfolio of common stocks, including the risk that the general level of stock prices may decline, thereby adversely affecting the value of each unit of the ETF. ETFs also involve the risk that an active trading market for an ETF’s shares may not develop or be maintained.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. The bar chart depicts the Fund’s performance during the period indicated. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the Fund’s performance during the period indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Fourth Quarter 2011 3.46%          Worst Quarter: Third Quarter 2011 -24.59%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Emerging Markets Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 3.39%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.44% [10]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 2.81% [10]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.63% [10]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 445
3 Years rr_ExpenseExampleYear03 1,343
5 Years rr_ExpenseExampleYear05 2,251
10 Years rr_ExpenseExampleYear10 4,566
Annual Total Returns rr_BarChartTableAbstract  
2011 rr_AnnualReturn2011 (23.92%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.59%)
Janus Emerging Markets Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (23.92%)
Since Inception rr_AverageAnnualReturnSinceInception (23.07%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (23.95%)
Since Inception rr_AverageAnnualReturnSinceInception (23.10%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (15.35%)
Since Inception rr_AverageAnnualReturnSinceInception (19.54%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Emerging Markets Fund | Class D Shares | Morgan Stanley Capital International Emerging Markets Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International Emerging Markets IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (18.42%)
Since Inception rr_AverageAnnualReturnSinceInception (16.45%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2010
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Life Sciences Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Life Sciences Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 54% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 54.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of companies that the portfolio manager believes have a life science orientation. Generally speaking, the “life sciences” relate to maintaining or improving quality of life. So, for example, companies with a “life science orientation” include companies engaged in research, development, production, or distribution of products or services related to health and personal care, medicine, or pharmaceuticals. The Fund implements this policy by investing primarily in equity securities of U.S. and foreign companies selected for their growth potential. The Fund normally invests in issuers from several different countries, which may include the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities. As a fundamental policy, the Fund normally invests at least 25% of its total assets in the “life sciences” sector, which may include companies in the following industry groups: health care; pharmaceuticals; agriculture; cosmetics/personal care; and biotechnology.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration As a fundamental policy, the Fund normally invests at least 25% of its total assets in the “life sciences” sector, which may include companies in the following industry groups: health care; pharmaceuticals; agriculture; cosmetics/personal care; and biotechnology.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 3.7% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Concentration Risk. The Fund focuses its investments in “life sciences” related industry groups. As a result, the Fund may be subject to greater risks and its net asset value may fluctuate more than a fund that does not concentrate its investments.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Third Quarter 2010 12.24%          Worst Quarter: Fourth Quarter 2008 -18.91%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.16%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.08%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 679
3 Years rr_ExpenseExampleYear03 899
5 Years rr_ExpenseExampleYear05 1,136
10 Years rr_ExpenseExampleYear10 1,816
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 679
3 Years rr_ExpenseExampleNoRedemptionYear03 899
5 Years rr_ExpenseExampleNoRedemptionYear05 1,136
10 Years rr_ExpenseExampleNoRedemptionYear10 1,816
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.78%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 281
3 Years rr_ExpenseExampleYear03 560
5 Years rr_ExpenseExampleYear05 964
10 Years rr_ExpenseExampleYear10 2,095
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 181
3 Years rr_ExpenseExampleNoRedemptionYear03 560
5 Years rr_ExpenseExampleNoRedemptionYear05 964
10 Years rr_ExpenseExampleNoRedemptionYear10 2,095
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.33%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.25%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 127
3 Years rr_ExpenseExampleYear03 397
5 Years rr_ExpenseExampleYear05 686
10 Years rr_ExpenseExampleYear10 1,511
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 127
3 Years rr_ExpenseExampleNoRedemptionYear03 397
5 Years rr_ExpenseExampleNoRedemptionYear05 686
10 Years rr_ExpenseExampleNoRedemptionYear10 1,511
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.24%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.88%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 90
3 Years rr_ExpenseExampleYear03 281
5 Years rr_ExpenseExampleYear05 488
10 Years rr_ExpenseExampleYear10 1,084
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 90
3 Years rr_ExpenseExampleNoRedemptionYear03 281
5 Years rr_ExpenseExampleNoRedemptionYear05 488
10 Years rr_ExpenseExampleNoRedemptionYear10 1,084
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.37%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.34%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.01%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 103
3 Years rr_ExpenseExampleYear03 322
5 Years rr_ExpenseExampleYear05 558
10 Years rr_ExpenseExampleYear10 1,236
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 103
3 Years rr_ExpenseExampleNoRedemptionYear03 322
5 Years rr_ExpenseExampleNoRedemptionYear05 558
10 Years rr_ExpenseExampleNoRedemptionYear10 1,236
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (30.11%)
2003 rr_AnnualReturn2003 27.44%
2004 rr_AnnualReturn2004 14.95%
2005 rr_AnnualReturn2005 11.45%
2006 rr_AnnualReturn2006 (1.95%)
2007 rr_AnnualReturn2007 22.53%
2008 rr_AnnualReturn2008 (28.77%)
2009 rr_AnnualReturn2009 26.30%
2010 rr_AnnualReturn2010 8.13%
2011 rr_AnnualReturn2011 7.18%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.24%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (18.91%)
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 0.94%
5 Years rr_AverageAnnualReturnYear05 3.69%
10 Years rr_AverageAnnualReturnYear10 2.90%
Since Inception rr_AverageAnnualReturnSinceInception 6.72%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 5.29%
5 Years rr_AverageAnnualReturnYear05 4.17%
10 Years rr_AverageAnnualReturnYear10 2.75%
Since Inception rr_AverageAnnualReturnSinceInception 6.43%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.92%
5 Years rr_AverageAnnualReturnYear05 4.74%
10 Years rr_AverageAnnualReturnYear10 3.34%
Since Inception rr_AverageAnnualReturnSinceInception 7.05%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.30%
5 Years rr_AverageAnnualReturnYear05 5.02%
10 Years rr_AverageAnnualReturnYear10 3.64%
Since Inception rr_AverageAnnualReturnSinceInception 7.35%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.18%
5 Years rr_AverageAnnualReturnYear05 5.02%
10 Years rr_AverageAnnualReturnYear10 3.64%
Since Inception rr_AverageAnnualReturnSinceInception 7.35%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 7.17%
5 Years rr_AverageAnnualReturnYear05 4.99%
10 Years rr_AverageAnnualReturnYear10 3.62%
Since Inception rr_AverageAnnualReturnSinceInception 7.33%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 4.67%
5 Years rr_AverageAnnualReturnYear05 4.32%
10 Years rr_AverageAnnualReturnYear10 3.16%
Since Inception rr_AverageAnnualReturnSinceInception 6.56%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.99%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International World Health Care Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Health Care Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 9.46%
5 Years rr_AverageAnnualReturnYear05 1.69%
10 Years rr_AverageAnnualReturnYear10 3.13%
Since Inception rr_AverageAnnualReturnSinceInception 2.28%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Life Sciences Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Life Sciences Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 54% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 54.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of companies that the portfolio manager believes have a life science orientation. Generally speaking, the “life sciences” relate to maintaining or improving quality of life. So, for example, companies with a “life science orientation” include companies engaged in research, development, production, or distribution of products or services related to health and personal care, medicine, or pharmaceuticals. The Fund implements this policy by investing primarily in equity securities of U.S. and foreign companies selected for their growth potential. The Fund normally invests in issuers from several different countries, which may include the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities. As a fundamental policy, the Fund normally invests at least 25% of its total assets in the “life sciences” sector, which may include companies in the following industry groups: health care; pharmaceuticals; agriculture; cosmetics/personal care; and biotechnology.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration As a fundamental policy, the Fund normally invests at least 25% of its total assets in the “life sciences” sector, which may include companies in the following industry groups: health care; pharmaceuticals; agriculture; cosmetics/personal care; and biotechnology.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 3.7% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Concentration Risk. The Fund focuses its investments in “life sciences” related industry groups. As a result, the Fund may be subject to greater risks and its net asset value may fluctuate more than a fund that does not concentrate its investments.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Third Quarter 2010 12.34%          Worst Quarter: Fourth Quarter 2008 -18.91%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Global Life Sciences Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.27%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.24%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 93
3 Years rr_ExpenseExampleYear03 290
5 Years rr_ExpenseExampleYear05 504
10 Years rr_ExpenseExampleYear10 1,120
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (30.11%)
2003 rr_AnnualReturn2003 27.44%
2004 rr_AnnualReturn2004 14.95%
2005 rr_AnnualReturn2005 11.45%
2006 rr_AnnualReturn2006 (1.95%)
2007 rr_AnnualReturn2007 22.53%
2008 rr_AnnualReturn2008 (28.77%)
2009 rr_AnnualReturn2009 26.30%
2010 rr_AnnualReturn2010 8.19%
2011 rr_AnnualReturn2011 7.30%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.34%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (18.91%)
Janus Global Life Sciences Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.30%
5 Years rr_AverageAnnualReturnYear05 5.06%
10 Years rr_AverageAnnualReturnYear10 3.66%
Since Inception rr_AverageAnnualReturnSinceInception 7.36%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 7.28%
5 Years rr_AverageAnnualReturnYear05 5.02%
10 Years rr_AverageAnnualReturnYear10 3.64%
Since Inception rr_AverageAnnualReturnSinceInception 7.35%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 4.78%
5 Years rr_AverageAnnualReturnYear05 4.35%
10 Years rr_AverageAnnualReturnYear10 3.17%
Since Inception rr_AverageAnnualReturnSinceInception 6.58%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.99%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Life Sciences Fund | Class D Shares | Morgan Stanley Capital International World Health Care Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Health Care Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 9.46%
5 Years rr_AverageAnnualReturnYear05 1.69%
10 Years rr_AverageAnnualReturnYear10 3.13%
Since Inception rr_AverageAnnualReturnSinceInception 2.28%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Research Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Research Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Research Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 78% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 78.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. The Fund may invest in companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The Fund normally invests at least 40% of its net assets in securities of issuers or companies from different countries located throughout the world, excluding the United States. The Fund may have significant exposure to emerging markets. The Fund may also invest in foreign equity and debt securities.

Janus Capital’s equity research analysts (the “Research Team”) select investments for the Fund which represent their high-conviction investment ideas in all market capitalizations, styles, and geographies. The Research Team, comprised of sector specialists, conducts fundamental analysis with a focus on “bottom up” research, quantitative modeling, and valuation analysis. Using this research process, analysts rate their stocks based upon attractiveness. Analysts bring their high-conviction ideas to their respective sector teams. Sector teams compare the appreciation and risk potential of each of the team’s high-conviction ideas and construct a sector portfolio that is intended to maximize the best risk-reward opportunities.

Positions may be sold when, among other things, there is no longer high conviction in the return potential of the investment or if the risk characteristics have caused a re-evaluation of the opportunity. This may occur if the stock has appreciated and reflects the anticipated value, if another company represents a better risk-reward opportunity, or if the investment’s fundamental characteristics deteriorate. Securities may also be sold from the portfolio to rebalance sector weightings.

Janus Capital’s Director of Equity Research oversees the investment process and is responsible for the day-to-day management of the Fund. It is expected that the Fund will be broadly diversified among a variety of industry sectors. The Fund intends to be fully invested under normal circumstances. However, under unusual circumstances, if the Research Team does not have high conviction in enough investment opportunities, the Fund’s uninvested assets may be held in cash or similar instruments.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions, or to hedge currency exposure relative to the Fund’s benchmark index) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 6.3% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the investment personnel’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the investment personnel’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities. The Fund compares and broadly matches its sector weights to those of a growth-based index. If growth stocks are out of favor, sectors that are larger in a growth index may underperform, leading to Fund underperformance relative to indices less biased toward growth stocks.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 24.54%          Worst Quarter: Fourth Quarter 2008 -24.95%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Research Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.75%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.17%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 687
3 Years rr_ExpenseExampleYear03 925
5 Years rr_ExpenseExampleYear05 1,182
10 Years rr_ExpenseExampleYear10 1,914
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 687
3 Years rr_ExpenseExampleNoRedemptionYear03 925
5 Years rr_ExpenseExampleNoRedemptionYear05 1,182
10 Years rr_ExpenseExampleNoRedemptionYear10 1,914
Janus Global Research Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.75%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.94%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 297
3 Years rr_ExpenseExampleYear03 609
5 Years rr_ExpenseExampleYear05 1,047
10 Years rr_ExpenseExampleYear10 2,264
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 197
3 Years rr_ExpenseExampleNoRedemptionYear03 609
5 Years rr_ExpenseExampleNoRedemptionYear05 1,047
10 Years rr_ExpenseExampleNoRedemptionYear10 2,264
Janus Global Research Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.75%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.36%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 138
3 Years rr_ExpenseExampleYear03 431
5 Years rr_ExpenseExampleYear05 745
10 Years rr_ExpenseExampleYear10 1,635
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 138
3 Years rr_ExpenseExampleNoRedemptionYear03 431
5 Years rr_ExpenseExampleNoRedemptionYear05 745
10 Years rr_ExpenseExampleNoRedemptionYear10 1,635
Janus Global Research Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.75%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.22%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.97%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 99
3 Years rr_ExpenseExampleYear03 309
5 Years rr_ExpenseExampleYear05 536
10 Years rr_ExpenseExampleYear10 1,190
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 99
3 Years rr_ExpenseExampleNoRedemptionYear03 309
5 Years rr_ExpenseExampleNoRedemptionYear05 536
10 Years rr_ExpenseExampleNoRedemptionYear10 1,190
Janus Global Research Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.75%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.11%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 113
3 Years rr_ExpenseExampleYear03 353
5 Years rr_ExpenseExampleYear05 612
10 Years rr_ExpenseExampleYear10 1,352
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 113
3 Years rr_ExpenseExampleNoRedemptionYear03 353
5 Years rr_ExpenseExampleNoRedemptionYear05 612
10 Years rr_ExpenseExampleNoRedemptionYear10 1,352
Annual Total Returns rr_BarChartTableAbstract  
2006 rr_AnnualReturn2006 18.40%
2007 rr_AnnualReturn2007 26.75%
2008 rr_AnnualReturn2008 (45.49%)
2009 rr_AnnualReturn2009 45.18%
2010 rr_AnnualReturn2010 20.62%
2011 rr_AnnualReturn2011 (7.59%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 24.54%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.95%)
Janus Global Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (12.99%)
5 Years rr_AverageAnnualReturnYear05 1.01%
Since Inception rr_AverageAnnualReturnSinceInception 5.86%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (9.35%)
5 Years rr_AverageAnnualReturnYear05 1.41%
Since Inception rr_AverageAnnualReturnSinceInception 5.96%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.83%)
5 Years rr_AverageAnnualReturnYear05 1.96%
Since Inception rr_AverageAnnualReturnSinceInception 6.52%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.47%)
5 Years rr_AverageAnnualReturnYear05 2.26%
Since Inception rr_AverageAnnualReturnSinceInception 6.81%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.59%)
5 Years rr_AverageAnnualReturnYear05 2.26%
Since Inception rr_AverageAnnualReturnSinceInception 6.81%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (7.61%)
5 Years rr_AverageAnnualReturnYear05 1.99%
Since Inception rr_AverageAnnualReturnSinceInception 6.25%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (4.91%)
5 Years rr_AverageAnnualReturnYear05 1.88%
Since Inception rr_AverageAnnualReturnSinceInception 5.71%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
Since Inception rr_AverageAnnualReturnSinceInception 2.71%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International World Growth Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Growth Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.49%)
5 Years rr_AverageAnnualReturnYear05 (0.52%)
Since Inception rr_AverageAnnualReturnSinceInception 3.05%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Research Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Research Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 78% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 78.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks selected for their growth potential. The Fund may invest in companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The Fund normally invests at least 40% of its net assets in securities of issuers or companies from different countries located throughout the world, excluding the United States. The Fund may have significant exposure to emerging markets. The Fund may also invest in foreign equity and debt securities.

Janus Capital’s equity research analysts (the “Research Team”) select investments for the Fund which represent their high-conviction investment ideas in all market capitalizations, styles, and geographies. The Research Team, comprised of sector specialists, conducts fundamental analysis with a focus on “bottom up” research, quantitative modeling, and valuation analysis. Using this research process, analysts rate their stocks based upon attractiveness. Analysts bring their high-conviction ideas to their respective sector teams. Sector teams compare the appreciation and risk potential of each of the team’s high-conviction ideas and construct a sector portfolio that is intended to maximize the best risk-reward opportunities.

Positions may be sold when, among other things, there is no longer high conviction in the return potential of the investment or if the risk characteristics have caused a re-evaluation of the opportunity. This may occur if the stock has appreciated and reflects the anticipated value, if another company represents a better risk-reward opportunity, or if the investment’s fundamental characteristics deteriorate. Securities may also be sold from the portfolio to rebalance sector weightings.

Janus Capital’s Director of Equity Research oversees the investment process and is responsible for the day-to-day management of the Fund. It is expected that the Fund will be broadly diversified among a variety of industry sectors. The Fund intends to be fully invested under normal circumstances. However, under unusual circumstances, if the Research Team does not have high conviction in enough investment opportunities, the Fund’s uninvested assets may be held in cash or similar instruments.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions, or to hedge currency exposure relative to the Fund’s benchmark index) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 6.3% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the investment personnel’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the investment personnel’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities. The Fund compares and broadly matches its sector weights to those of a growth-based index. If growth stocks are out of favor, sectors that are larger in a growth index may underperform, leading to Fund underperformance relative to indices less biased toward growth stocks.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 24.54%          Worst Quarter: Fourth Quarter 2008 -24.95%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Global Research Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.75%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.01%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 103
3 Years rr_ExpenseExampleYear03 322
5 Years rr_ExpenseExampleYear05 558
10 Years rr_ExpenseExampleYear10 1,236
Annual Total Returns rr_BarChartTableAbstract  
2006 rr_AnnualReturn2006 18.40%
2007 rr_AnnualReturn2007 26.75%
2008 rr_AnnualReturn2008 (45.49%)
2009 rr_AnnualReturn2009 45.18%
2010 rr_AnnualReturn2010 20.70%
2011 rr_AnnualReturn2011 (7.48%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 24.54%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.95%)
Janus Global Research Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (7.48%)
5 Years rr_AverageAnnualReturnYear05 2.30%
Since Inception rr_AverageAnnualReturnSinceInception 6.84%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (7.52%)
5 Years rr_AverageAnnualReturnYear05 2.03%
Since Inception rr_AverageAnnualReturnSinceInception 6.28%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (4.81%)
5 Years rr_AverageAnnualReturnYear05 1.91%
Since Inception rr_AverageAnnualReturnSinceInception 5.73%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class D Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
Since Inception rr_AverageAnnualReturnSinceInception 2.71%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Research Fund | Class D Shares | Morgan Stanley Capital International World Growth Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Growth Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.49%)
5 Years rr_AverageAnnualReturnYear05 (0.52%)
Since Inception rr_AverageAnnualReturnSinceInception 3.05%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2005
Janus Global Select Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Select Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Select Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 138% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 138.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing primarily in a core group of 30-50 domestic and foreign common stocks selected for their growth potential and normally investing at least 40% of its net assets in securities of issuers from different countries located throughout the world, excluding the United States. The Fund may invest in companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in U.S. and foreign debt securities. The Fund may have significant exposure to emerging markets. As of September 30, 2011, the Fund held stocks of 38 companies. Of these holdings, 30 comprised approximately 86.59% of the Fund’s holdings.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts. The Fund may use derivatives for different purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, to adjust its currency exposure relative to its benchmark index, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund invests primarily in common stocks, which tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 18.3% of the Fund’s investments were in emerging markets.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.

Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.71%          Worst Quarter: Fourth Quarter 2008 -32.29%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.20%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.09%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 680
3 Years rr_ExpenseExampleYear03 902
5 Years rr_ExpenseExampleYear05 1,141
10 Years rr_ExpenseExampleYear10 1,827
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 680
3 Years rr_ExpenseExampleNoRedemptionYear03 902
5 Years rr_ExpenseExampleNoRedemptionYear05 1,141
10 Years rr_ExpenseExampleNoRedemptionYear10 1,827
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.82%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 285
3 Years rr_ExpenseExampleYear03 573
5 Years rr_ExpenseExampleYear05 985
10 Years rr_ExpenseExampleYear10 2,137
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 185
3 Years rr_ExpenseExampleNoRedemptionYear03 573
5 Years rr_ExpenseExampleNoRedemptionYear05 985
10 Years rr_ExpenseExampleNoRedemptionYear10 2,137
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.33%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.22%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 124
3 Years rr_ExpenseExampleYear03 387
5 Years rr_ExpenseExampleYear05 670
10 Years rr_ExpenseExampleYear10 1,477
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 124
3 Years rr_ExpenseExampleNoRedemptionYear03 387
5 Years rr_ExpenseExampleNoRedemptionYear05 670
10 Years rr_ExpenseExampleNoRedemptionYear10 1,477
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.21%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.85%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 87
3 Years rr_ExpenseExampleYear03 271
5 Years rr_ExpenseExampleYear05 471
10 Years rr_ExpenseExampleYear10 1,049
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 87
3 Years rr_ExpenseExampleNoRedemptionYear03 271
5 Years rr_ExpenseExampleNoRedemptionYear05 471
10 Years rr_ExpenseExampleNoRedemptionYear10 1,049
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.33%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.47%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 150
3 Years rr_ExpenseExampleYear03 465
5 Years rr_ExpenseExampleYear05 803
10 Years rr_ExpenseExampleYear10 1,757
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 150
3 Years rr_ExpenseExampleNoRedemptionYear03 465
5 Years rr_ExpenseExampleNoRedemptionYear05 803
10 Years rr_ExpenseExampleNoRedemptionYear10 1,757
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.33%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.97%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 99
3 Years rr_ExpenseExampleYear03 309
5 Years rr_ExpenseExampleYear05 536
10 Years rr_ExpenseExampleYear10 1,190
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 99
3 Years rr_ExpenseExampleNoRedemptionYear03 309
5 Years rr_ExpenseExampleNoRedemptionYear05 536
10 Years rr_ExpenseExampleNoRedemptionYear10 1,190
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (29.77%)
2003 rr_AnnualReturn2003 43.81%
2004 rr_AnnualReturn2004 14.90%
2005 rr_AnnualReturn2005 20.93%
2006 rr_AnnualReturn2006 18.64%
2007 rr_AnnualReturn2007 32.38%
2008 rr_AnnualReturn2008 (49.78%)
2009 rr_AnnualReturn2009 54.74%
2010 rr_AnnualReturn2010 20.01%
2011 rr_AnnualReturn2011 (17.84%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.71%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (32.29%)
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (22.68%)
5 Years rr_AverageAnnualReturnYear05 (0.98%)
10 Years rr_AverageAnnualReturnYear10 4.71%
Since Inception rr_AverageAnnualReturnSinceInception (0.44%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (19.39%)
5 Years rr_AverageAnnualReturnYear05 (0.56%)
10 Years rr_AverageAnnualReturnYear10 4.53%
Since Inception rr_AverageAnnualReturnSinceInception (0.68%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (18.07%)
5 Years rr_AverageAnnualReturnYear05 0.04%
10 Years rr_AverageAnnualReturnYear10 5.13%
Since Inception rr_AverageAnnualReturnSinceInception (0.12%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (17.88%)
5 Years rr_AverageAnnualReturnYear05 0.29%
10 Years rr_AverageAnnualReturnYear10 5.38%
Since Inception rr_AverageAnnualReturnSinceInception 0.11%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (18.34%)
5 Years rr_AverageAnnualReturnYear05 (0.23%)
10 Years rr_AverageAnnualReturnYear10 4.86%
Since Inception rr_AverageAnnualReturnSinceInception (0.37%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (17.84%)
5 Years rr_AverageAnnualReturnYear05 0.29%
10 Years rr_AverageAnnualReturnYear10 5.38%
Since Inception rr_AverageAnnualReturnSinceInception 0.11%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (17.86%)
5 Years rr_AverageAnnualReturnYear05 0.20%
10 Years rr_AverageAnnualReturnYear10 5.31%
Since Inception rr_AverageAnnualReturnSinceInception 0.04%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (11.32%)
5 Years rr_AverageAnnualReturnYear05 0.26%
10 Years rr_AverageAnnualReturnYear10 4.71%
Since Inception rr_AverageAnnualReturnSinceInception 0.09%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 0.99%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Select Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Select Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 138% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 138.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by normally investing primarily in a core group of 30-50 domestic and foreign common stocks selected for their growth potential and normally investing at least 40% of its net assets in securities of issuers from different countries located throughout the world, excluding the United States. The Fund may invest in companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in U.S. and foreign debt securities. The Fund may have significant exposure to emerging markets. As of September 30, 2011, the Fund held stocks of 38 companies. Of these holdings, 30 comprised approximately 86.59% of the Fund’s holdings.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts. The Fund may use derivatives for different purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, to adjust its currency exposure relative to its benchmark index, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund invests primarily in common stocks, which tend to be more volatile than many other investment choices.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 18.3% of the Fund’s investments were in emerging markets.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio manager more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. The index is not actively managed and is not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.71%          Worst Quarter: Fourth Quarter 2008 -32.29%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Global Select Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.22%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.01%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.86%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 88
3 Years rr_ExpenseExampleYear03 274
5 Years rr_ExpenseExampleYear05 477
10 Years rr_ExpenseExampleYear10 1,061
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (29.77%)
2003 rr_AnnualReturn2003 43.81%
2004 rr_AnnualReturn2004 14.90%
2005 rr_AnnualReturn2005 20.93%
2006 rr_AnnualReturn2006 18.64%
2007 rr_AnnualReturn2007 32.38%
2008 rr_AnnualReturn2008 (49.78%)
2009 rr_AnnualReturn2009 54.74%
2010 rr_AnnualReturn2010 20.12%
2011 rr_AnnualReturn2011 (17.72%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.71%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (32.29%)
Janus Global Select Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (17.72%)
5 Years rr_AverageAnnualReturnYear05 0.34%
10 Years rr_AverageAnnualReturnYear10 5.41%
Since Inception rr_AverageAnnualReturnSinceInception 0.13%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (17.75%)
5 Years rr_AverageAnnualReturnYear05 0.24%
10 Years rr_AverageAnnualReturnYear10 5.33%
Since Inception rr_AverageAnnualReturnSinceInception 0.06%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (11.22%)
5 Years rr_AverageAnnualReturnYear05 0.30%
10 Years rr_AverageAnnualReturnYear10 4.74%
Since Inception rr_AverageAnnualReturnSinceInception 0.10%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Select Fund | Class D Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 0.99%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2000
Janus Global Technology Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Technology Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Technology Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 89% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 89.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of companies that the portfolio manager believes will benefit significantly from advances or improvements in technology. These companies generally fall into two categories:

• companies that the portfolio manager believes have or will develop products, processes, or services that will provide significant technological advancements or improvements; and

• companies that the portfolio manager believes rely extensively on technology in connection with their operations or services.

The Fund implements this policy by investing primarily in equity securities of U.S. and foreign companies selected for their growth potential. The Fund normally invests in issuers from several different countries, which may include the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 4.2% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Industry Risk. Although the Fund does not concentrate its investments in specific industries, it may invest in companies related in such a way that they react similarly to certain market pressures. As a result, the Fund’s returns may be considerably more volatile than the returns of a fund that does not invest in similarly related companies.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.

Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.81%          Worst Quarter: Fourth Quarter 2008 -25.94%

Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Global Technology Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.24%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.13%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 684
3 Years rr_ExpenseExampleYear03 913
5 Years rr_ExpenseExampleYear05 1,161
10 Years rr_ExpenseExampleYear10 1,871
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 684
3 Years rr_ExpenseExampleNoRedemptionYear03 913
5 Years rr_ExpenseExampleNoRedemptionYear05 1,161
10 Years rr_ExpenseExampleNoRedemptionYear10 1,871
Janus Global Technology Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.85%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 288
3 Years rr_ExpenseExampleYear03 582
5 Years rr_ExpenseExampleYear05 1,001
10 Years rr_ExpenseExampleYear10 2,169
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 188
3 Years rr_ExpenseExampleNoRedemptionYear03 582
5 Years rr_ExpenseExampleNoRedemptionYear05 1,001
10 Years rr_ExpenseExampleNoRedemptionYear10 2,169
Janus Global Technology Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.37%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.34%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.26%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 128
3 Years rr_ExpenseExampleYear03 400
5 Years rr_ExpenseExampleYear05 692
10 Years rr_ExpenseExampleYear10 1,523
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 128
3 Years rr_ExpenseExampleNoRedemptionYear03 400
5 Years rr_ExpenseExampleNoRedemptionYear05 692
10 Years rr_ExpenseExampleNoRedemptionYear10 1,523
Janus Global Technology Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.24%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.88%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 90
3 Years rr_ExpenseExampleYear03 281
5 Years rr_ExpenseExampleYear05 488
10 Years rr_ExpenseExampleYear10 1,084
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 90
3 Years rr_ExpenseExampleNoRedemptionYear03 281
5 Years rr_ExpenseExampleNoRedemptionYear05 488
10 Years rr_ExpenseExampleNoRedemptionYear10 1,084
Janus Global Technology Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.37%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.34%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.01%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 103
3 Years rr_ExpenseExampleYear03 322
5 Years rr_ExpenseExampleYear05 558
10 Years rr_ExpenseExampleYear10 1,236
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 103
3 Years rr_ExpenseExampleNoRedemptionYear03 322
5 Years rr_ExpenseExampleNoRedemptionYear05 558
10 Years rr_ExpenseExampleNoRedemptionYear10 1,236
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (40.94%)
2003 rr_AnnualReturn2003 47.14%
2004 rr_AnnualReturn2004 1.23%
2005 rr_AnnualReturn2005 11.50%
2006 rr_AnnualReturn2006 7.98%
2007 rr_AnnualReturn2007 21.88%
2008 rr_AnnualReturn2008 (43.27%)
2009 rr_AnnualReturn2009 57.29%
2010 rr_AnnualReturn2010 24.57%
2011 rr_AnnualReturn2011 (8.54%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.81%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.94%)
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (13.94%)
5 Years rr_AverageAnnualReturnYear05 3.07%
10 Years rr_AverageAnnualReturnYear10 2.05%
Since Inception rr_AverageAnnualReturnSinceInception 3.22%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (10.25%)
5 Years rr_AverageAnnualReturnYear05 3.53%
10 Years rr_AverageAnnualReturnYear10 1.91%
Since Inception rr_AverageAnnualReturnSinceInception 2.94%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.75%)
5 Years rr_AverageAnnualReturnYear05 4.14%
10 Years rr_AverageAnnualReturnYear10 2.51%
Since Inception rr_AverageAnnualReturnSinceInception 3.54%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.45%)
5 Years rr_AverageAnnualReturnYear05 4.38%
10 Years rr_AverageAnnualReturnYear10 2.76%
Since Inception rr_AverageAnnualReturnSinceInception 3.82%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.54%)
5 Years rr_AverageAnnualReturnYear05 4.38%
10 Years rr_AverageAnnualReturnYear10 2.76%
Since Inception rr_AverageAnnualReturnSinceInception 3.82%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (8.54%)
5 Years rr_AverageAnnualReturnYear05 4.37%
10 Years rr_AverageAnnualReturnYear10 2.75%
Since Inception rr_AverageAnnualReturnSinceInception 3.75%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (5.55%)
5 Years rr_AverageAnnualReturnYear05 3.77%
10 Years rr_AverageAnnualReturnYear10 2.38%
Since Inception rr_AverageAnnualReturnSinceInception 3.31%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.99%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International World Information Technology Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Information Technology Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.49%)
5 Years rr_AverageAnnualReturnYear05 1.18%
10 Years rr_AverageAnnualReturnYear10 1.26%
Since Inception rr_AverageAnnualReturnSinceInception (0.55%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Global Technology Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Global Technology Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 89% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 89.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of companies that the portfolio manager believes will benefit significantly from advances or improvements in technology. These companies generally fall into two categories:

• companies that the portfolio manager believes have or will develop products, processes, or services that will provide significant technological advancements or improvements; and

• companies that the portfolio manager believes rely extensively on technology in connection with their operations or services.

The Fund implements this policy by investing primarily in equity securities of U.S. and foreign companies selected for their growth potential. The Fund normally invests in issuers from several different countries, which may include the United States.

The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may also invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 4.2% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Industry Risk. Although the Fund does not concentrate its investments in specific industries, it may invest in companies related in such a way that they react similarly to certain market pressures. As a result, the Fund’s returns may be considerably more volatile than the returns of a fund that does not invest in similarly related companies.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.81%           Worst Quarter: Fourth Quarter 2008 -25.94%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Global Technology Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.28%
Short Sale Dividend Expenses rr_Component1OtherExpensesOverAssets 0.03%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.92%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 94
3 Years rr_ExpenseExampleYear03 293
5 Years rr_ExpenseExampleYear05 509
10 Years rr_ExpenseExampleYear10 1,131
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (40.94%)
2003 rr_AnnualReturn2003 47.14%
2004 rr_AnnualReturn2004 1.23%
2005 rr_AnnualReturn2005 11.50%
2006 rr_AnnualReturn2006 7.98%
2007 rr_AnnualReturn2007 21.88%
2008 rr_AnnualReturn2008 (43.27%)
2009 rr_AnnualReturn2009 57.29%
2010 rr_AnnualReturn2010 24.64%
2011 rr_AnnualReturn2011 (8.41%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.81%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.94%)
Janus Global Technology Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (8.41%)
5 Years rr_AverageAnnualReturnYear05 4.42%
10 Years rr_AverageAnnualReturnYear10 2.78%
Since Inception rr_AverageAnnualReturnSinceInception 3.84%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (8.41%)
5 Years rr_AverageAnnualReturnYear05 4.41%
10 Years rr_AverageAnnualReturnYear10 2.77%
Since Inception rr_AverageAnnualReturnSinceInception 3.76%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (5.47%)
5 Years rr_AverageAnnualReturnYear05 3.80%
10 Years rr_AverageAnnualReturnYear10 2.40%
Since Inception rr_AverageAnnualReturnSinceInception 3.32%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class D Shares | S&P 500® Index
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel S&P 500® Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.99%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus Global Technology Fund | Class D Shares | Morgan Stanley Capital International World Information Technology Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World Information Technology Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.49%)
5 Years rr_AverageAnnualReturnYear05 1.18%
10 Years rr_AverageAnnualReturnYear10 1.26%
Since Inception rr_AverageAnnualReturnSinceInception (0.55%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1998
Janus International Equity Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus International Equity Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus International Equity Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 77% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 77.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in equity securities. The Fund normally invests in a core group of 60-100 equity securities of issuers from different countries located throughout the world, excluding the United States. The Fund may, under unusual circumstances, invest all of its assets in a single country. The Fund may invest in emerging markets but will normally limit such investments to 20% of its net assets, measured at the time of purchase. The Fund may also invest in foreign debt securities.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio managers normally seek to limit any sector exposure and country exposure to plus or minus 10% of the respective weighting of the Fund’s primary benchmark index, currently the Morgan Stanley Capital International EAFE® Index.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. As of September 30, 2011, approximately 12.0% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser International Equity Fund (“JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares prior to the reorganization, calculated using the fees and expenses of each respective share class of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class T Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares prior to the reorganization, calculated using the fees and expenses of Class T Shares, without the effect of any fee and expense limitations or waivers.

If Class T Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class I Shares, Class A Shares, Class C Shares, Class S Shares, Class R Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class I Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 31.95%          Worst Quarter: Third Quarter 2008 -24.25%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class I Shares for periods following July 6, 2009; and for the JAD predecessor fund’s Class I Shares for periods prior to July 6, 2009. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.23%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 693
3 Years rr_ExpenseExampleYear03 943
5 Years rr_ExpenseExampleYear05 1,212
10 Years rr_ExpenseExampleYear10 1,978
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 693
3 Years rr_ExpenseExampleNoRedemptionYear03 943
5 Years rr_ExpenseExampleNoRedemptionYear05 1,212
10 Years rr_ExpenseExampleNoRedemptionYear10 1,978
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.99%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 302
3 Years rr_ExpenseExampleYear03 624
5 Years rr_ExpenseExampleYear05 1,073
10 Years rr_ExpenseExampleYear10 2,317
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 202
3 Years rr_ExpenseExampleNoRedemptionYear03 624
5 Years rr_ExpenseExampleNoRedemptionYear05 1,073
10 Years rr_ExpenseExampleNoRedemptionYear10 2,317
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.39%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 142
3 Years rr_ExpenseExampleYear03 440
5 Years rr_ExpenseExampleYear05 761
10 Years rr_ExpenseExampleYear10 1,669
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 142
3 Years rr_ExpenseExampleNoRedemptionYear03 440
5 Years rr_ExpenseExampleNoRedemptionYear05 761
10 Years rr_ExpenseExampleNoRedemptionYear10 1,669
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.13%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 93
3 Years rr_ExpenseExampleYear03 290
5 Years rr_ExpenseExampleYear05 504
10 Years rr_ExpenseExampleYear10 1,120
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 93
3 Years rr_ExpenseExampleNoRedemptionYear03 290
5 Years rr_ExpenseExampleNoRedemptionYear05 504
10 Years rr_ExpenseExampleNoRedemptionYear10 1,120
Annual Total Returns rr_BarChartTableAbstract  
2007 rr_AnnualReturn2007 22.23%
2008 rr_AnnualReturn2008 (45.99%)
2009 rr_AnnualReturn2009 52.08%
2010 rr_AnnualReturn2010 14.30%
2011 rr_AnnualReturn2011 (13.67%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 31.95%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.25%)
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.64%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 167
3 Years rr_ExpenseExampleYear03 517
5 Years rr_ExpenseExampleYear05 892
10 Years rr_ExpenseExampleYear10 1,944
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 167
3 Years rr_ExpenseExampleNoRedemptionYear03 517
5 Years rr_ExpenseExampleNoRedemptionYear05 892
10 Years rr_ExpenseExampleNoRedemptionYear10 1,944
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.78%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.35%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.13%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 115
3 Years rr_ExpenseExampleYear03 359
5 Years rr_ExpenseExampleYear05 622
10 Years rr_ExpenseExampleYear10 1,375
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 115
3 Years rr_ExpenseExampleNoRedemptionYear03 359
5 Years rr_ExpenseExampleNoRedemptionYear05 622
10 Years rr_ExpenseExampleNoRedemptionYear10 1,375
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (18.88%)
5 Years rr_AverageAnnualReturnYear05 (1.61%)
Since Inception rr_AverageAnnualReturnSinceInception (0.58%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (15.45%)
5 Years rr_AverageAnnualReturnYear05 (1.29%)
Since Inception rr_AverageAnnualReturnSinceInception (0.28%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (14.14%)
5 Years rr_AverageAnnualReturnYear05 (0.40%)
Since Inception rr_AverageAnnualReturnSinceInception 0.62%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.67%)
5 Years rr_AverageAnnualReturnYear05 (0.19%)
Since Inception rr_AverageAnnualReturnSinceInception 0.83%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (14.29%)
5 Years rr_AverageAnnualReturnYear05 (0.98%)
Since Inception rr_AverageAnnualReturnSinceInception 0.03%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.88%)
5 Years rr_AverageAnnualReturnYear05 (0.37%)
Since Inception rr_AverageAnnualReturnSinceInception 0.65%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.76%)
5 Years rr_AverageAnnualReturnYear05 (0.35%)
Since Inception rr_AverageAnnualReturnSinceInception 0.67%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.45%)
5 Years rr_AverageAnnualReturnYear05 (0.11%)
Since Inception rr_AverageAnnualReturnSinceInception 0.76%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International EAFE® Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International EAFE® Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (12.14%)
5 Years rr_AverageAnnualReturnYear05 (4.72%)
Since Inception rr_AverageAnnualReturnSinceInception (3.68%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World ex-U.S. Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World ex-U.S. IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (13.71%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
Since Inception rr_AverageAnnualReturnSinceInception (1.90%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus International Equity Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus International Equity Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 77% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 77.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in equity securities. The Fund normally invests in a core group of 60-100 equity securities of issuers from different countries located throughout the world, excluding the United States. The Fund may, under unusual circumstances, invest all of its assets in a single country. The Fund may invest in emerging markets but will normally limit such investments to 20% of its net assets, measured at the time of purchase. The Fund may also invest in foreign debt securities.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio managers normally seek to limit any sector exposure and country exposure to plus or minus 10% of the respective weighting of the Fund’s primary benchmark index, currently the Morgan Stanley Capital International EAFE® Index.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. As of September 30, 2011, approximately 12.0% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s Class I Shares calculated using the fees and expenses of Class D Shares, without the effect of any fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 31.92%          Worst Quarter: Third Quarter 2008 -24.25%

Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class I Shares for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus International Equity Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.78%
Other Expenses rr_OtherExpensesOverAssets 0.38%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.16%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 118
3 Years rr_ExpenseExampleYear03 368
5 Years rr_ExpenseExampleYear05 638
10 Years rr_ExpenseExampleYear10 1,409
Annual Total Returns rr_BarChartTableAbstract  
2007 rr_AnnualReturn2007 22.23%
2008 rr_AnnualReturn2008 (45.99%)
2009 rr_AnnualReturn2009 51.91%
2010 rr_AnnualReturn2010 14.30%
2011 rr_AnnualReturn2011 (13.77%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 31.92%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.25%)
Janus International Equity Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.77%)
5 Years rr_AverageAnnualReturnYear05 (0.21%)
Since Inception rr_AverageAnnualReturnSinceInception 0.81%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.83%)
5 Years rr_AverageAnnualReturnYear05 (0.37%)
Since Inception rr_AverageAnnualReturnSinceInception 0.66%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.55%)
5 Years rr_AverageAnnualReturnYear05 (0.13%)
Since Inception rr_AverageAnnualReturnSinceInception 0.74%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class D Shares | Morgan Stanley Capital International EAFE® Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International EAFE® Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (12.14%)
5 Years rr_AverageAnnualReturnYear05 (4.72%)
Since Inception rr_AverageAnnualReturnSinceInception (3.68%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus International Equity Fund | Class D Shares | Morgan Stanley Capital International All Country World ex-U.S. Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World ex-U.S. IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (13.71%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
Since Inception rr_AverageAnnualReturnSinceInception (1.90%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 28, 2006
Janus Overseas Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Overseas Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Overseas Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 43% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 43.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of issuers from countries outside of the United States. The Fund normally invests in securities of issuers from several different countries, excluding the United States. Although the Fund typically invests 80% or more of its assets in issuers located outside the United States, it also may normally invest up to 20% of its assets, measured at the time of purchase, in U.S. issuers, and it may, under unusual circumstances, invest all or substantially all of its assets in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 31.1% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 36.78%           Worst Quarter: Fourth Quarter 2008 -27.94%

Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.04%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 675
3 Years rr_ExpenseExampleYear03 887
5 Years rr_ExpenseExampleYear05 1,116
10 Years rr_ExpenseExampleYear10 1,773
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 675
3 Years rr_ExpenseExampleNoRedemptionYear03 887
5 Years rr_ExpenseExampleNoRedemptionYear05 1,116
10 Years rr_ExpenseExampleNoRedemptionYear10 1,773
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.78%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 281
3 Years rr_ExpenseExampleYear03 560
5 Years rr_ExpenseExampleYear05 964
10 Years rr_ExpenseExampleYear10 2,095
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 181
3 Years rr_ExpenseExampleNoRedemptionYear03 560
5 Years rr_ExpenseExampleNoRedemptionYear05 964
10 Years rr_ExpenseExampleNoRedemptionYear10 2,095
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.19%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 121
3 Years rr_ExpenseExampleYear03 378
5 Years rr_ExpenseExampleYear05 654
10 Years rr_ExpenseExampleYear10 1,443
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 121
3 Years rr_ExpenseExampleNoRedemptionYear03 378
5 Years rr_ExpenseExampleNoRedemptionYear05 654
10 Years rr_ExpenseExampleNoRedemptionYear10 1,443
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.12%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.76%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 78
3 Years rr_ExpenseExampleYear03 243
5 Years rr_ExpenseExampleYear05 422
10 Years rr_ExpenseExampleYear10 942
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 78
3 Years rr_ExpenseExampleNoRedemptionYear03 243
5 Years rr_ExpenseExampleNoRedemptionYear05 422
10 Years rr_ExpenseExampleNoRedemptionYear10 942
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.44%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 147
3 Years rr_ExpenseExampleYear03 456
5 Years rr_ExpenseExampleYear05 787
10 Years rr_ExpenseExampleYear10 1,724
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 147
3 Years rr_ExpenseExampleNoRedemptionYear03 456
5 Years rr_ExpenseExampleNoRedemptionYear05 787
10 Years rr_ExpenseExampleNoRedemptionYear10 1,724
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.94%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 96
3 Years rr_ExpenseExampleYear03 300
5 Years rr_ExpenseExampleYear05 520
10 Years rr_ExpenseExampleYear10 1,155
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 96
3 Years rr_ExpenseExampleNoRedemptionYear03 300
5 Years rr_ExpenseExampleNoRedemptionYear05 520
10 Years rr_ExpenseExampleNoRedemptionYear10 1,155
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (23.89%)
2003 rr_AnnualReturn2003 36.79%
2004 rr_AnnualReturn2004 18.58%
2005 rr_AnnualReturn2005 32.39%
2006 rr_AnnualReturn2006 47.21%
2007 rr_AnnualReturn2007 27.76%
2008 rr_AnnualReturn2008 (52.75%)
2009 rr_AnnualReturn2009 78.12%
2010 rr_AnnualReturn2010 19.28%
2011 rr_AnnualReturn2011 (32.78%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 36.78%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.94%)
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (36.74%)
5 Years rr_AverageAnnualReturnYear05 (4.17%)
10 Years rr_AverageAnnualReturnYear10 6.82%
Since Inception rr_AverageAnnualReturnSinceInception 9.36%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (33.99%)
5 Years rr_AverageAnnualReturnYear05 (3.77%)
10 Years rr_AverageAnnualReturnYear10 6.65%
Since Inception rr_AverageAnnualReturnSinceInception 9.01%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (32.92%)
5 Years rr_AverageAnnualReturnYear05 (3.19%)
10 Years rr_AverageAnnualReturnYear10 7.26%
Since Inception rr_AverageAnnualReturnSinceInception 9.57%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (32.70%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
10 Years rr_AverageAnnualReturnYear10 7.57%
Since Inception rr_AverageAnnualReturnSinceInception 9.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (33.11%)
5 Years rr_AverageAnnualReturnYear05 (3.44%)
10 Years rr_AverageAnnualReturnYear10 6.99%
Since Inception rr_AverageAnnualReturnSinceInception 9.32%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (32.78%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
10 Years rr_AverageAnnualReturnYear10 7.57%
Since Inception rr_AverageAnnualReturnSinceInception 9.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (33.47%)
5 Years rr_AverageAnnualReturnYear05 (3.60%)
10 Years rr_AverageAnnualReturnYear10 7.13%
Since Inception rr_AverageAnnualReturnSinceInception 9.21%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (20.16%)
5 Years rr_AverageAnnualReturnYear05 (2.40%)
10 Years rr_AverageAnnualReturnYear10 6.73%
Since Inception rr_AverageAnnualReturnSinceInception 8.78%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International EAFE® Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International EAFE® Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (12.14%)
5 Years rr_AverageAnnualReturnYear05 (4.72%)
10 Years rr_AverageAnnualReturnYear10 4.67%
Since Inception rr_AverageAnnualReturnSinceInception 3.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World ex-U.S. Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World ex-U.S. IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (13.71%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
10 Years rr_AverageAnnualReturnYear10 6.31%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Overseas Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Overseas Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 43% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 43.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests, under normal circumstances, at least 80% of its net assets in securities of issuers from countries outside of the United States. The Fund normally invests in securities of issuers from several different countries, excluding the United States. Although the Fund typically invests 80% or more of its assets in issuers located outside the United States, it also may normally invest up to 20% of its assets, measured at the time of purchase, in U.S. issuers, and it may, under unusual circumstances, invest all or substantially all of its assets in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) for different purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions) and to earn income and enhance returns. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 31.1% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 36.78%          Worst Quarter: Fourth Quarter 2008 -27.94%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Overseas Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.83%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 85
3 Years rr_ExpenseExampleYear03 265
5 Years rr_ExpenseExampleYear05 460
10 Years rr_ExpenseExampleYear10 1,025
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (23.89%)
2003 rr_AnnualReturn2003 36.79%
2004 rr_AnnualReturn2004 18.58%
2005 rr_AnnualReturn2005 32.39%
2006 rr_AnnualReturn2006 47.21%
2007 rr_AnnualReturn2007 27.76%
2008 rr_AnnualReturn2008 (52.75%)
2009 rr_AnnualReturn2009 78.12%
2010 rr_AnnualReturn2010 19.39%
2011 rr_AnnualReturn2011 (32.71%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 36.78%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.94%)
Janus Overseas Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (32.71%)
5 Years rr_AverageAnnualReturnYear05 (2.88%)
10 Years rr_AverageAnnualReturnYear10 7.59%
Since Inception rr_AverageAnnualReturnSinceInception 9.84%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (33.40%)
5 Years rr_AverageAnnualReturnYear05 (3.56%)
10 Years rr_AverageAnnualReturnYear10 7.15%
Since Inception rr_AverageAnnualReturnSinceInception 9.22%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (20.12%)
5 Years rr_AverageAnnualReturnYear05 (2.37%)
10 Years rr_AverageAnnualReturnYear10 6.75%
Since Inception rr_AverageAnnualReturnSinceInception 8.79%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class D Shares | Morgan Stanley Capital International EAFE® Index (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International EAFE® Index (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (12.14%)
5 Years rr_AverageAnnualReturnYear05 (4.72%)
10 Years rr_AverageAnnualReturnYear10 4.67%
Since Inception rr_AverageAnnualReturnSinceInception 3.83%
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Overseas Fund | Class D Shares | Morgan Stanley Capital International All Country World ex-U.S. Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World ex-U.S. IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (13.71%)
5 Years rr_AverageAnnualReturnYear05 (2.92%)
10 Years rr_AverageAnnualReturnYear10 6.31%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate May 02, 1994
Janus Worldwide Fund | Class A, C, S, I, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Worldwide Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Worldwide Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 80 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 94% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 94.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in equity securities, which include, but are not limited to, common stocks, preferred stocks, and depositary receipts of companies of any size located throughout the world. The Fund normally invests in issuers from several different countries, including the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in foreign equity and debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest a significant portion of its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions) including, but not limited to, put and call options, swaps, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund may also invest in derivative instruments for other purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions). For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 6.2% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class R Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 23.17%          Worst Quarter: Fourth Quarter 2008 -23.27%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.09%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 680
3 Years rr_ExpenseExampleYear03 902
5 Years rr_ExpenseExampleYear05 1,141
10 Years rr_ExpenseExampleYear10 1,827
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 680
3 Years rr_ExpenseExampleNoRedemptionYear03 902
5 Years rr_ExpenseExampleNoRedemptionYear05 1,141
10 Years rr_ExpenseExampleNoRedemptionYear10 1,827
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.18%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.84%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 287
3 Years rr_ExpenseExampleYear03 579
5 Years rr_ExpenseExampleYear05 995
10 Years rr_ExpenseExampleYear10 2,159
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 187
3 Years rr_ExpenseExampleNoRedemptionYear03 579
5 Years rr_ExpenseExampleNoRedemptionYear05 995
10 Years rr_ExpenseExampleNoRedemptionYear10 2,159
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.22%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 124
3 Years rr_ExpenseExampleYear03 387
5 Years rr_ExpenseExampleYear05 670
10 Years rr_ExpenseExampleYear10 1,477
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 124
3 Years rr_ExpenseExampleNoRedemptionYear03 387
5 Years rr_ExpenseExampleNoRedemptionYear05 670
10 Years rr_ExpenseExampleNoRedemptionYear10 1,477
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.77%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 79
3 Years rr_ExpenseExampleYear03 246
5 Years rr_ExpenseExampleYear05 428
10 Years rr_ExpenseExampleYear10 954
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 79
3 Years rr_ExpenseExampleNoRedemptionYear03 246
5 Years rr_ExpenseExampleNoRedemptionYear05 428
10 Years rr_ExpenseExampleNoRedemptionYear10 954
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class R
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class R
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class R
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.47%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class R Shares
1 Year rr_ExpenseExampleYear01 150
3 Years rr_ExpenseExampleYear03 465
5 Years rr_ExpenseExampleYear05 803
10 Years rr_ExpenseExampleYear10 1,757
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 150
3 Years rr_ExpenseExampleNoRedemptionYear03 465
5 Years rr_ExpenseExampleNoRedemptionYear05 803
10 Years rr_ExpenseExampleNoRedemptionYear10 1,757
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.66%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.97%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 99
3 Years rr_ExpenseExampleYear03 309
5 Years rr_ExpenseExampleYear05 536
10 Years rr_ExpenseExampleYear10 1,190
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 99
3 Years rr_ExpenseExampleNoRedemptionYear03 309
5 Years rr_ExpenseExampleNoRedemptionYear05 536
10 Years rr_ExpenseExampleNoRedemptionYear10 1,190
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (26.01%)
2003 rr_AnnualReturn2003 24.23%
2004 rr_AnnualReturn2004 5.54%
2005 rr_AnnualReturn2005 5.84%
2006 rr_AnnualReturn2006 17.90%
2007 rr_AnnualReturn2007 9.23%
2008 rr_AnnualReturn2008 (45.02%)
2009 rr_AnnualReturn2009 37.68%
2010 rr_AnnualReturn2010 15.62%
2011 rr_AnnualReturn2011 (13.85%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 23.17%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.27%)
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (18.90%)
5 Years rr_AverageAnnualReturnYear05 (4.78%)
10 Years rr_AverageAnnualReturnYear10 (0.56%)
Since Inception rr_AverageAnnualReturnSinceInception 7.18%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (15.45%)
5 Years rr_AverageAnnualReturnYear05 (4.37%)
10 Years rr_AverageAnnualReturnYear10 (0.74%)
Since Inception rr_AverageAnnualReturnSinceInception 6.79%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (14.05%)
5 Years rr_AverageAnnualReturnYear05 (3.81%)
10 Years rr_AverageAnnualReturnYear10 (0.16%)
Since Inception rr_AverageAnnualReturnSinceInception 7.33%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.64%)
5 Years rr_AverageAnnualReturnYear05 (3.81%)
10 Years rr_AverageAnnualReturnYear10 (0.03%)
Since Inception rr_AverageAnnualReturnSinceInception 7.46%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class R
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class R Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (14.27%)
5 Years rr_AverageAnnualReturnYear05 (4.04%)
10 Years rr_AverageAnnualReturnYear10 (0.40%)
Since Inception rr_AverageAnnualReturnSinceInception 7.11%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.85%)
5 Years rr_AverageAnnualReturnYear05 (3.81%)
10 Years rr_AverageAnnualReturnYear10 (0.03%)
Since Inception rr_AverageAnnualReturnSinceInception 7.46%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.94%)
5 Years rr_AverageAnnualReturnYear05 (3.91%)
10 Years rr_AverageAnnualReturnYear10 (0.15%)
Since Inception rr_AverageAnnualReturnSinceInception 6.79%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.87%)
5 Years rr_AverageAnnualReturnYear05 (3.19%)
10 Years rr_AverageAnnualReturnYear10 (0.01%)
Since Inception rr_AverageAnnualReturnSinceInception 6.46%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class A, C, S, I, R, T Shares | Morgan Stanley Capital International World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.54%)
5 Years rr_AverageAnnualReturnYear05 (2.37%)
10 Years rr_AverageAnnualReturnYear10 3.62%
Since Inception rr_AverageAnnualReturnSinceInception 5.98%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Worldwide Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Worldwide Fund seeks long-term growth of capital.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 94% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 94.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in equity securities, which include, but are not limited to, common stocks, preferred stocks, and depositary receipts of companies of any size located throughout the world. The Fund normally invests in issuers from several different countries, including the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in foreign equity and debt securities.

The portfolio manager applies a “bottom up” approach in choosing investments. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may invest a significant portion of its assets in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as equity securities, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions) including, but not limited to, put and call options, swaps, and forward currency contracts to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund may also invest in derivative instruments for other purposes, including hedging (to offset risks associated with an investment, currency exposure, or market conditions). For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2011, approximately 6.2% of the Fund’s investments were in emerging markets.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: Second Quarter 2009 23.17%          Worst Quarter: Fourth Quarter 2008 -23.27%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Janus Worldwide Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.66%
Other Expenses rr_OtherExpensesOverAssets 0.21%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.87%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 89
3 Years rr_ExpenseExampleYear03 278
5 Years rr_ExpenseExampleYear05 482
10 Years rr_ExpenseExampleYear10 1,073
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (26.01%)
2003 rr_AnnualReturn2003 24.23%
2004 rr_AnnualReturn2004 5.54%
2005 rr_AnnualReturn2005 5.84%
2006 rr_AnnualReturn2006 17.90%
2007 rr_AnnualReturn2007 9.23%
2008 rr_AnnualReturn2008 (45.02%)
2009 rr_AnnualReturn2009 37.68%
2010 rr_AnnualReturn2010 15.70%
2011 rr_AnnualReturn2011 (13.74%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 23.17%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.27%)
Janus Worldwide Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (13.74%)
5 Years rr_AverageAnnualReturnYear05 (3.77%)
10 Years rr_AverageAnnualReturnYear10 (0.01%)
Since Inception rr_AverageAnnualReturnSinceInception 7.47%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (13.85%)
5 Years rr_AverageAnnualReturnYear05 (3.88%)
10 Years rr_AverageAnnualReturnYear10 (0.13%)
Since Inception rr_AverageAnnualReturnSinceInception 6.80%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 (8.78%)
5 Years rr_AverageAnnualReturnYear05 (3.16%)
10 Years rr_AverageAnnualReturnYear10 0.01%
Since Inception rr_AverageAnnualReturnSinceInception 6.47%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class D Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception   
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Worldwide Fund | Class D Shares | Morgan Stanley Capital International World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.54%)
5 Years rr_AverageAnnualReturnYear05 (2.37%)
10 Years rr_AverageAnnualReturnYear10 3.62%
Since Inception rr_AverageAnnualReturnSinceInception 5.98%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1991
Janus Protected Series - Growth | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Protected Series – Growth
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Protected Series – Growth seeks long-term growth of capital and capital preservation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 37 of the Fund’s Prospectus and in the “Purchases” section on page 59 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses, including the maximum amount of the capital protection fee, without waivers, remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 362% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 362.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks growth of capital to the extent consistent with maintaining protection against significant downside movement of the net asset value (“NAV”) per share of each share class of the Fund. Specifically, the portfolio manager manages the Fund’s assets in an effort to ensure that the NAV for any share class will not fall below 80% of the highest NAV attained separately by each share class during the life of the Fund, reduced for dividends, distributions, any extraordinary expenses, and certain extraordinary items (for each share class, the “Protected NAV”). A reduction of the NAV can be described further by using distributions as an example. In the event the Fund declares dividends from net investment income and capital gains distributions, which normally occurs in December, the Protected NAV per share will be adjusted down so that the relative protection level remains at the level in place prior to the distribution. While the Protected NAV per share is changed as a result of a distribution, the protected value of your account balance does not change, assuming you reinvest your distribution. For example, on a day the highest NAV per share of a share class is reached at $11.00, the Protected NAV per share is set at $8.80, which is 80% of the highest NAV per share. When the highest NAV per share increases to $12.50, the Protected NAV per share is set at $10.00, which is 80% of the highest NAV. On a day the NAV per share is $12.00, the Fund declares a per share distribution of $1.00. The result of the distribution is that the NAV per share is reduced from $12.00 to $11.00. The Protected NAV per share is also reduced so that the Protected NAV per share is the same relative to the post-distribution NAV per share of $11.00 as it was to the pre-distribution NAV per share of $12.00. The Protected NAV per share of $10.00 was 83.3% of the pre-distribution NAV per share of $12.00 per share and the post-distribution Protected NAV per share is adjusted to $9.17, which is 83.3% of the post-distribution NAV per share. Additional information regarding how the Protected NAV per share is adjusted following a distribution is included in Appendix A. The reduction for extraordinary expenses and extraordinary items from the NAV would have a similar result on the Protected NAV.

In general, protection for the Fund means, as the NAV per share for a share class rises, the Protected NAV also rises and becomes the new Protected NAV regardless of whether the share class’ NAV per share subsequently declines or fails to achieve a new high threshold. However, as a share class’ NAV declines towards the Protected NAV, more of the Fund’s assets will be comprised of cash and other investments, called the “Protection Component,” as further described below.

In order to minimize the effect of equity market volatility on the NAV per share for a share class, the Fund allocates its portfolio assets between two investment components. Through its first component, the “Equity Component,” the Fund seeks to achieve growth of capital by investing primarily in common stocks selected for their growth potential. Although the Fund may invest in companies of any size, it generally invests in larger, more established companies. The Equity Component may also consist of derivatives such as swaps, futures, and options. Through its second component, the “Protection Component,” the Fund seeks to limit downside risk by investing in cash and other investments including, but not limited to, money market instruments, U.S. Treasuries, and other equity market risk reducing instruments, such as short index futures. Due to equity market conditions and the Fund’s overall risk profile, the amount of Fund assets allocated to the Protection Component may, at times, be significant. The Fund’s allocation between the Equity Component and the Protection Component will vary over time. Up to 100% of assets may be allocated to either component.

The portfolio manager applies a “bottom up” approach in choosing common stock investments for the Equity Component. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. As part of the Equity Component, the Fund may invest in foreign equity and debt securities, which may include investments in emerging markets.

As noted above, the Fund may also invest the assets of either component in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as stocks, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) including, but not limited to, swaps, futures, and over-the-counter and exchange-traded put or call options for various purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, to earn income and enhance returns, and/or to invest in volatility (such as exposure to a volatility index). The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

In an effort to protect against significant downward movement of the NAV per share for a share class, the Fund has entered into a Capital Protection Agreement with BNP Paribas Prime Brokerage, Inc., a U.S. registered broker-dealer (the “Capital Protection Provider”). Pursuant to the Capital Protection Agreement, under certain conditions, the Capital Protection Provider will provide capital protection to the Fund (the “Protection”) in the event that any share class’ NAV per share falls below its Protected NAV. Any one share class falling below its Protected NAV will trigger the Protection and liquidation of the Fund and each of its share classes, regardless of whether the NAV of any other share class is above its Protected NAV. The Capital Protection Provider has agreed to initially extend $1.5 billion in aggregate protection coverage to the Fund with such amount being reviewed periodically to determine whether additional coverage is necessary or available to support the Fund’s rising assets (the “Maximum Settlement Amount”). As such, under the Capital Protection Agreement, the NAV of each share class is protected to at least the Protected NAV for such share class, subject to an aggregate limit on the overall payout to the Fund of the Maximum Settlement Amount. In the event that the Protection is triggered, meaning at least one share class’ NAV is below its Protected NAV, the Capital Protection Provider is obligated to pay the Fund the “Settlement Amount,” which is the lesser of (i) the sum of the shortfall amounts per share class (the “Aggregate Shortfall Amount”) and (ii) the Maximum Settlement Amount. For each share class, the shortfall amount is calculated by first establishing, among those share classes that have a NAV below their Protected NAV, the highest percentage difference among all of those share classes between the Protected NAV per share and the then-current NAV per share, and applying that percentage to each Fund share class’ then-current NAV per share. The Aggregate Shortfall Amount is thus allocated on a pro rata basis to each share class.

In order to comply with the terms of the Capital Protection Agreement, the Fund must provide certain information to the Capital Protection Provider and the Fund’s portfolio manager is required to manage the Fund within certain risk parameters as identified on a daily basis by the Capital Protection Provider based on a risk allocation methodology. This risk allocation methodology factors in, among other things, market volatility, the Fund’s exposure to industries, sectors, or countries, and liquidity of the Fund’s holdings. In general, as equity markets are rising, the Fund’s allocation to the Equity Component will rise with a goal of taking advantage of any potential future market increase, and as equity markets are falling, the Fund’s portfolio manager will allocate more of the Fund’s assets to the Protection Component in an effort to protect the Fund from potential ongoing decreases in the market. The Fund’s asset allocation will vary over time depending on equity market conditions and the Fund’s portfolio composition. As a result, the Fund’s allocation to each investment component could change as frequently as daily, resulting in a higher portfolio turnover rate than other mutual funds.

The Capital Protection Agreement has an initial term of 10 years and may be extended for additional 10-year terms by mutual agreement of the Fund and the Capital Protection Provider. Under certain circumstances, the Capital Protection Agreement may be terminated prior to the expiration of any effective term, which in any case would become the “Termination Date.” Only shareholders who hold their shares on such Termination Date are entitled to receive the Protected NAV from the Fund.

In the event of such termination of the Capital Protection Agreement, the Fund will terminate and liquidate and the Capital Protection Provider will pay the Fund any amounts due related to the Protection. This Prospectus serves as advance notice to you of any such liquidation. There are limited circumstances in which the Protection also terminates on the Termination Date, meaning the Capital Protection Provider is not obligated to pay any amounts to the Fund even where the NAV of a share class is below its Protected NAV. These circumstances are described further below under “Principal Investment Risks” as “Capital Protection Termination Risk.”

It is important to understand that the Capital Protection Agreement is a financial product that is intended to protect the Fund against significant market declines and does not in any way constitute any form of insurance. In addition, the Capital Protection Provider is not an insurance company or an insurance provider, nor is it acting as an adviser or subadviser for the Fund.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money, despite the Capital Protection Agreement. Common stocks tend to be more volatile than many other investment choices. Because the NAV per share for a share class is protected to at least 80%, and not 100%, of its highest attained NAV since the inception of the share class (as reduced to account for dividends, distributions, any extraordinary expenses, and certain extraordinary items), it is possible that in the event that equity markets fall, you could lose money, even if the Protection is triggered. In addition, if the Capital Protection Agreement does not work as intended or has been terminated, you could lose money. Because the Protected NAV is reduced by dividends, distributions, any extraordinary expenses, and certain extraordinary items, the amount of Protection could be less than 80% of the highest attained NAV for your class of shares, meaning the Protected NAV does not become a static number that only increases. To the extent that the protected amount owed to the Fund exceeds the Maximum Settlement Amount ($1.5 billion), none of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares will cover any shortfall amount, so you could lose money including amounts that would have otherwise been protected.

The Protected NAV for each share class will be posted on the Janus websites at janus.com/advisor/mutual-funds, or janus.com/allfunds for shareholders of Class D Shares. Any change to the Protected NAV is expected to be updated within one business day. Because any one share class falling below its Protected NAV can alone trigger the Protection and liquidation of the Fund, shareholders should review the Protected NAV for each share class prior to purchasing shares of this Fund, keeping in mind that each share class has different fees and expenses that impact the NAV. Shareholders considering an investment in Class A Shares should pay particular attention to the Protected NAV of each share class as part of their investment decision given that Class A Shares have an upfront sales load that once paid, is not reimbursed when the Fund liquidates.

Allocation Risk. Because there are risk parameters within which the portfolio manager must manage the Fund’s assets in order to maintain the Protection, the Fund’s ability to take certain investment actions that the portfolio manager might otherwise take may be limited. More specifically, complying with the provisions of the Capital Protection Agreement may impact the Fund’s allocation of assets to and within the Equity Component during the life of the Fund, may not allow the Fund to be fully invested in the Equity Component, and/or may affect the portfolio manager’s ability to respond to changing equity market conditions. This could limit the Fund’s ability to capture certain market gains when the allocations are more heavily weighted to the Protection Component. Conversely, as equity markets are rising or displaying signs of relative stability, the Fund may have more of the portfolio weighted towards assets considered to have higher risk which could increase the potential for loss of return for the Fund. Generally, the risk parameters may lead the portfolio manager to take certain investment actions that he otherwise would not take when allocating the Fund’s assets between and within the Equity Component and the Protection Component. This allocation process can have an adverse effect on the performance of the Fund, especially during periods of increased equity market volatility. The risk allocation methodology is designed so that the NAV of each share class does not fall below its Protected NAV and, if successful, protection payments are not triggered. It is possible, however, that the risk allocation methodology may not work as designed or intended and may cause the Fund to trigger the Protection, resulting in the termination of the Fund. In addition, the allocation of the Fund’s assets between and within the Equity Component and the Protection Component will likely result in a high portfolio turnover rate and additional transaction costs, such as brokerage commissions, which can impact the Fund’s returns. Because the portfolio manager allocates the Fund’s assets between and within the Equity Component and Protection Component daily according to a risk allocation methodology, there is the risk that a sudden intraday market drop may occur before the Fund’s Equity Component exposure can be reduced. Additionally, if the Fund fails to allocate its assets according to the risk allocation methodology, the Capital Protection Provider will have the option to terminate the Capital Protection Agreement, resulting in the Fund allocating 100% of its assets solely to cash and the liquidation of the Fund. Under these circumstances, the Capital Protection Provider will pay any amounts it is obligated to pay to the Fund.

Market Underperformance Risk. The Fund’s use of the risk allocation methodology and the resulting allocation between and within the Equity Component and the Protection Component may cause the Fund to underperform its primary benchmark and/or other similarly situated growth funds. This underperformance may be a result of the portfolio manager’s inability to reallocate Fund assets to respond to rising equity market conditions as quickly as another fund that invests primarily in equity securities. In addition, to maintain compliance with the risk parameters, the Fund may need to liquidate a position, or forego an investment that could have otherwise contributed to Fund performance. Under certain circumstances, the Capital Protection Agreement may require that all of the Fund’s assets be fully allocated to the Protection Component, thus limiting the upside potential for Fund returns during this period. The use of the risk allocation methodology may also impact the Fund’s performance in the event that it does not work as intended, potentially subjecting the Fund to additional expenses as a result of increased trading or allocating a larger portion of the Fund’s assets than necessary to either the Equity Component or Protection Component. Because the Fund may reallocate its assets between and within the Equity Component and the Protection Component as frequently as daily, the Fund’s reallocation will likely cause it to experience an increase in its portfolio turnover rate resulting in higher costs, which may have a negative effect on the Fund’s performance, particularly during periods of relative instability in equity markets. The Fund’s payment of the capital protection fee to the Capital Protection Provider may also result in the Fund underperforming its primary benchmark and/or other similarly situated growth funds that do not pay a protection fee.

Capital Protection Termination Risk. There is a risk that the Protection could terminate without any obligation of the Capital Protection Provider or the Parent Guarantor to make payment to the Fund. The terms and conditions of the Capital Protection Agreement are designed to protect against certain market risks inherent in any equity investment. It does not protect against certain actions or omissions that constitute gross negligence, fraud, bad faith, willful misconduct, or a criminal act on the part of the Fund, Janus Capital or certain key employees of Janus Capital, or the Fund’s custodian, that negatively impacts a share class’ NAV. Such events will result in the termination of the Protection without any obligation by the Capital Protection Provider, and therefore by the Parent Guarantor, to make any payment to the Fund. The Fund will liquidate in these events, and shareholders will not receive the Protected NAV but will instead receive the Fund’s then-current NAV at the time their shares are redeemed, which may be lower than the Protected NAV and lower than the price per share of the shareholder’s initial investment. None of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares is obligated to make any payment to the Fund or cover any shortfall. Therefore, in the event that the Protection is terminated as a result of such events, you could lose money as a result of the Fund losing the Protection under the Capital Protection Agreement, including amounts that would have otherwise been protected. This means that you could receive less than 80% of your investment and will not be reimbursed for any amounts paid under the Capital Protection Agreement.

Early Termination Events Risk. While the Capital Protection Agreement has an initial 10-year term that may be extended, there is a risk that the Capital Protection Agreement could terminate earlier under various scenarios at the option of the Capital Protection Provider, which are considered Early Termination Events. In such events, the Capital Protection Provider will be obligated to make the payment of the Settlement Amount, if due, to the Fund and the Fund will liquidate. Shareholders receive the higher of their Protected NAV or the then-current NAV for their share class, which will include any Settlement Amount due to the Fund. Examples of “Early Termination Events” include, but are not limited to (1) if the Fund, Janus Capital, or the Fund’s custodian, fails to comply with certain terms and conditions of the Capital Protection Agreement, including the failure to reallocate Fund assets when such assets fall outside the specified risk parameters, or (2) if the aggregate value of the Fund’s shares outstanding results in the Protection exceeding the Maximum Settlement Amount. The Fund is also expected to liquidate and the Capital Protection Agreement will terminate if, pursuant to the terms of the Capital Protection Agreement, the Protection is triggered. In addition, to the extent that the introduction of laws or a change of law, in each case, not known as of the date of the Capital Protection Agreement, results in a new or increased cost of capital or collateral for the Capital Protection Provider or its parent company, the Fund’s Board of Trustees will make a determination whether to approve the Fund paying such increased costs to the Capital Protection Provider or to terminate the Capital Protection Agreement. Only shareholders who hold their shares on the Termination Date are entitled to receive the Protected NAV from the Fund. Shareholders who redeem prior to the Termination Date receive the then-current NAV which will be higher than the Protected NAV for their share class and will not include any payment of the Protection.

Maximum Settlement Amount Risk. The Capital Protection Agreement currently covers the outstanding shares of each class of shares offered by the Fund having an aggregate protected amount up to an initial value of $1.5 billion. If the Maximum Settlement Amount exceeds $1.5 billion without any additional coverage being extended to the Fund, the Capital Protection Provider will not be liable for any Settlement Amount payment in excess of $1.5 billion. None of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares will be responsible for any portion of the Settlement Amount, including any amounts which may exceed the Maximum Settlement Amount. Therefore, although the Protection applies, you could lose money to the extent the Aggregate Shortfall Amount exceeds the Maximum Settlement Amount including amounts that would have otherwise been protected. This means that you could receive less than 80% of your investment. In any event, as the Fund’s assets grow, the Fund intends to take such actions as may be deemed necessary, including limiting shareholder purchases, to limit the Aggregate Shortfall Amount to a level so that it does not exceed the Maximum Settlement Amount, but there is no guarantee that such efforts will be successful. There is no guarantee that the Capital Protection Provider will agree to extend coverage beyond $1.5 billion.

Liquidation Risk. Although the risk allocation methodology is designed so that the NAV of each share class does not fall below its Protected NAV, there is the possibility that the risk allocation methodology may not work as designed or redemptions, particularly a large redemption, may impact the allocation process, and the NAV of any share class falls below its Protected NAV. If this happens, it is expected that the Fund will receive payment of the Settlement Amount from the Capital Protection Provider, if due, and liquidate as soon as possible following the event. The NAV of one share class falling below its Protected NAV will result in the Protection being triggered and, as a result, the liquidation of the entire Fund, even though the NAV of one or more other share classes remains at or above its Protected NAV. Other events described in this Prospectus may, at the discretion of the Fund or Capital Protection Provider, as applicable, also terminate the Capital Protection Agreement resulting in payment of the Settlement Amount and liquidation of the Fund. In the event the Protection is triggered and the Fund begins the liquidation process, no other purchases will be permitted, and the payment of redemption proceeds will be suspended, likely from the day the Protection is triggered; shareholders receive the higher of their Protected NAV or the then-current NAV for their share class, which will include any Settlement Amount due to the Fund. Redemptions are taxable events. This Prospectus serves as advance notice to shareholders of any rejection of purchases, suspension of the payment of redemption proceeds, and liquidation of the Fund. In the event that the Capital Protection Agreement is terminated and the Fund begins the liquidation process, Janus Capital will make such information available at janus.com/advisor/mutual-funds, or janus.com/allfunds for shareholders of Class D Shares. Notice of the Fund liquidation will otherwise be made when you receive your redemption proceeds. For illustrative purposes to understand a scenario where the Protection is triggered and the Fund proceeds to liquidation, see below:

Protected NAV across all share classes is $10.00 –

• Day 1 (Tuesday) – One share class NAV is $9.00 and each other share class’ NAV is $11.00. Purchases are rejected and the payment of redemptions is suspended as the Fund proceeds to liquidation since there is at least one share class’ NAV that is below its Protected NAV.

• Day 7 (Monday) – Fund receives Protection payment from the Capital Protection Provider, and the Fund liquidates and terminates and pays out a $10.00 Protected NAV to the share class that had a $9.00 NAV. All other share classes are redeemed at $11.00 NAV, plus the Settlement Amount distributed pro rata to their share class.

Opportunity Cost Risk. It is possible that under the terms of the Capital Protection Agreement, the Fund’s allocation to the Equity Component could drop to a low level or be eliminated altogether, especially during periods of heightened volatility in equity markets. This would reduce the Fund’s ability to participate in upward equity market movements, and therefore, represents loss of opportunity compared to a fund that is fully invested in equity securities.

Counterparty Risk (Capital Protection Provider and its Parent Company). A shareholder’s ability to receive the Protected NAV from the Fund is dependent on the Fund’s ability to collect the Settlement Amount from the Capital Protection Provider pursuant to the terms of the Capital Protection Agreement or from the Capital Protection Provider’s parent under a separate parent guaranty. Fund transactions involving a counterparty, such as the Capital Protection Provider, are subject to the risk that the counterparty or a third party will not fulfill its obligation to the Fund (“counterparty risk”). Counterparty risk may arise because of the counterparty’s financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. As such, the Fund’s ability to benefit from the Protection may depend on the Capital Protection Provider’s, as well as its parent company’s, financial condition. As an added measure of protection, BNP Paribas, the parent company of the Capital Protection Provider, has issued an absolute, irrevocable and continuing guaranty pursuant to which it guarantees any and all financial obligations of the Capital Protection Provider under the Capital Protection Agreement. There is, however, a risk that the Capital Protection Provider’s parent company may not fulfill its obligations under the guaranty it has issued.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The Fund’s use of the risk allocation methodology is intended to protect against significant downward movement of the NAV per share for a share class, particularly in times of heightened volatility in the equity markets, but the methodology may not protect the Fund if equity markets take a sudden and/or significant fall.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations to the Fund. If the counterparty to a derivative transaction defaults, such as the Capital Protection Provider or Parent Guarantor, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders. The risk allocation methodology utilized by the Fund will likely increase the level of portfolio turnover.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money, despite the Capital Protection Agreement.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The Fund does not have a full calendar year of operations. Performance information for certain periods is included in the Fund’s first annual and/or semiannual report.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess The Fund does not have a full calendar year of operations.
Janus Protected Series - Growth | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.50%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.75%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.39% [11]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.59% [11]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.80% [11]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 897
3 Years rr_ExpenseExampleYear03 1,557
5 Years rr_ExpenseExampleYear05 2,238
10 Years rr_ExpenseExampleYear10 4,039
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 897
3 Years rr_ExpenseExampleNoRedemptionYear03 1,557
5 Years rr_ExpenseExampleNoRedemptionYear05 2,238
10 Years rr_ExpenseExampleNoRedemptionYear10 4,039
Janus Protected Series - Growth | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 2.48%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.73%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 4.12% [11]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.57% [11]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 2.55% [11]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 514
3 Years rr_ExpenseExampleYear03 1,252
5 Years rr_ExpenseExampleYear05 2,106
10 Years rr_ExpenseExampleYear10 4,306
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 414
3 Years rr_ExpenseExampleNoRedemptionYear03 1,252
5 Years rr_ExpenseExampleNoRedemptionYear05 2,106
10 Years rr_ExpenseExampleNoRedemptionYear10 4,306
Janus Protected Series - Growth | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 2.64%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.89%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.53% [11]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.49% [11]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 2.04% [11]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 356
3 Years rr_ExpenseExampleYear03 1,083
5 Years rr_ExpenseExampleYear05 1,831
10 Years rr_ExpenseExampleYear10 3,801
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 356
3 Years rr_ExpenseExampleNoRedemptionYear03 1,083
5 Years rr_ExpenseExampleNoRedemptionYear05 1,831
10 Years rr_ExpenseExampleNoRedemptionYear10 3,801
Janus Protected Series - Growth | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.48%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.73%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.12% [11]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.57% [11]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.55% [11]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 315
3 Years rr_ExpenseExampleYear03 963
5 Years rr_ExpenseExampleYear05 1,635
10 Years rr_ExpenseExampleYear10 3,430
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 315
3 Years rr_ExpenseExampleNoRedemptionYear03 963
5 Years rr_ExpenseExampleNoRedemptionYear05 1,635
10 Years rr_ExpenseExampleNoRedemptionYear10 3,430
Janus Protected Series - Growth | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.64%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 2.62%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 1.87%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.26% [11]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.47% [11]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.79% [11]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 329
3 Years rr_ExpenseExampleYear03 1,004
5 Years rr_ExpenseExampleYear05 1,702
10 Years rr_ExpenseExampleYear10 3,558
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 329
3 Years rr_ExpenseExampleNoRedemptionYear03 1,004
5 Years rr_ExpenseExampleNoRedemptionYear05 1,702
10 Years rr_ExpenseExampleNoRedemptionYear10 3,558
Janus Protected Series - Growth | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Janus Protected Series – Growth
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Protected Series – Growth seeks long-term growth of capital and capital preservation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2013
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses, including the maximum amount of the capital protection fee, without waivers, remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 362% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 362.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks growth of capital to the extent consistent with maintaining protection against significant downside movement of the net asset value (“NAV”) per share of each share class of the Fund. Specifically, the portfolio manager manages the Fund’s assets in an effort to ensure that the NAV for any share class will not fall below 80% of the highest NAV attained separately by each share class during the life of the Fund, reduced for dividends, distributions, any extraordinary expenses, and certain extraordinary items (for each share class, the “Protected NAV”). A reduction of the NAV can be described further by using distributions as an example. In the event the Fund declares dividends from net investment income and capital gains distributions, which normally occurs in December, the Protected NAV per share will be adjusted down so that the relative protection level remains at the level in place prior to the distribution. While the Protected NAV per share is changed as a result of a distribution, the protected value of your account balance does not change, assuming you reinvest your distribution. For example, on a day the highest NAV per share of a share class is reached at $11.00, the Protected NAV per share is set at $8.80, which is 80% of the highest NAV per share. When the highest NAV per share increases to $12.50, the Protected NAV per share is set at $10.00, which is 80% of the highest NAV. On a day the NAV per share is $12.00, the Fund declares a per share distribution of $1.00. The result of the distribution is that the NAV per share is reduced from $12.00 to $11.00. The Protected NAV per share is also reduced so that the Protected NAV per share is the same relative to the post-distribution NAV per share of $11.00 as it was to the pre-distribution NAV per share of $12.00. The Protected NAV per share of $10.00 was 83.3% of the pre-distribution NAV per share of $12.00 per share and the post-distribution Protected NAV per share is adjusted to $9.17, which is 83.3% of the post-distribution NAV per share. Additional information regarding how the Protected NAV per share is adjusted following a distribution is included in Appendix A. The reduction for extraordinary expenses and extraordinary items from the NAV would have a similar result on the Protected NAV.

In general, protection for the Fund means, as the NAV per share for a share class rises, the Protected NAV also rises and becomes the new Protected NAV regardless of whether the share class’ NAV per share subsequently declines or fails to achieve a new high threshold. However, as a share class’ NAV declines towards the Protected NAV, more of the Fund’s assets will be comprised of cash and other investments, called the “Protection Component,” as further described below.

In order to minimize the effect of equity market volatility on the NAV per share for a share class, the Fund allocates its portfolio assets between two investment components. Through its first component, the “Equity Component,” the Fund seeks to achieve growth of capital by investing primarily in common stocks selected for their growth potential. Although the Fund may invest in companies of any size, it generally invests in larger, more established companies. The Equity Component may also consist of derivatives such as swaps, futures, and options. Through its second component, the “Protection Component,” the Fund seeks to limit downside risk by investing in cash and other investments including, but not limited to, money market instruments, U.S. Treasuries, and other equity market risk reducing instruments, such as short index futures. Due to equity market conditions and the Fund’s overall risk profile, the amount of Fund assets allocated to the Protection Component may, at times, be significant. The Fund’s allocation between the Equity Component and the Protection Component will vary over time. Up to 100% of assets may be allocated to either component.

The portfolio manager applies a “bottom up” approach in choosing common stock investments for the Equity Component. In other words, the portfolio manager looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. As part of the Equity Component, the Fund may invest in foreign equity and debt securities, which may include investments in emerging markets.

As noted above, the Fund may also invest the assets of either component in derivatives, which are instruments that have a value derived from or directly linked to an underlying asset, such as stocks, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund may invest in derivative instruments (by taking long and/or short positions) including, but not limited to, swaps, futures, and over-the-counter and exchange-traded put or call options for various purposes, including hedging, to increase or decrease the Fund’s exposure to a particular market, to manage or adjust the risk profile of the Fund related to an investment or currency exposure, to earn income and enhance returns, and/or to invest in volatility (such as exposure to a volatility index). The Fund’s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times. For more information on the Fund’s use of derivatives, refer to the Fund’s shareholder reports and Form N-Q reports, which are filed with the Securities and Exchange Commission.

In an effort to protect against significant downward movement of the NAV per share for a share class, the Fund has entered into a Capital Protection Agreement with BNP Paribas Prime Brokerage, Inc., a U.S. registered broker-dealer (the “Capital Protection Provider”). Pursuant to the Capital Protection Agreement, under certain conditions, the Capital Protection Provider will provide capital protection to the Fund (the “Protection”) in the event that any share class’ NAV per share falls below its Protected NAV. Any one share class falling below its Protected NAV will trigger the Protection and liquidation of the Fund and each of its share classes, regardless of whether the NAV of any other share class is above its Protected NAV. The Capital Protection Provider has agreed to initially extend $1.5 billion in aggregate protection coverage to the Fund with such amount being reviewed periodically to determine whether additional coverage is necessary or available to support the Fund’s rising assets (the “Maximum Settlement Amount”). As such, under the Capital Protection Agreement, the NAV of each share class is protected to at least the Protected NAV for such share class, subject to an aggregate limit on the overall payout to the Fund of the Maximum Settlement Amount. In the event that the Protection is triggered, meaning at least one share class’ NAV is below its Protected NAV, the Capital Protection Provider is obligated to pay the Fund the “Settlement Amount,” which is the lesser of (i) the sum of the shortfall amounts per share class (the “Aggregate Shortfall Amount”) and (ii) the Maximum Settlement Amount. For each share class, the shortfall amount is calculated by first establishing, among those share classes that have a NAV below their Protected NAV, the highest percentage difference among all of those share classes between the Protected NAV per share and the then-current NAV per share, and applying that percentage to each Fund share class’ then-current NAV per share. The Aggregate Shortfall Amount is thus allocated on a pro rata basis to each share class.

In order to comply with the terms of the Capital Protection Agreement, the Fund must provide certain information to the Capital Protection Provider and the Fund’s portfolio manager is required to manage the Fund within certain risk parameters as identified on a daily basis by the Capital Protection Provider based on a risk allocation methodology. This risk allocation methodology factors in, among other things, market volatility, the Fund’s exposure to industries, sectors, or countries, and liquidity of the Fund’s holdings. In general, as equity markets are rising, the Fund’s allocation to the Equity Component will rise with a goal of taking advantage of any potential future market increase, and as equity markets are falling, the Fund’s portfolio manager will allocate more of the Fund’s assets to the Protection Component in an effort to protect the Fund from potential ongoing decreases in the market. The Fund’s asset allocation will vary over time depending on equity market conditions and the Fund’s portfolio composition. As a result, the Fund’s allocation to each investment component could change as frequently as daily, resulting in a higher portfolio turnover rate than other mutual funds.

The Capital Protection Agreement has an initial term of 10 years and may be extended for additional 10-year terms by mutual agreement of the Fund and the Capital Protection Provider. Under certain circumstances, the Capital Protection Agreement may be terminated prior to the expiration of any effective term, which in any case would become the “Termination Date.” Only shareholders who hold their shares on such Termination Date are entitled to receive the Protected NAV from the Fund. In the event of such termination of the Capital Protection Agreement, the Fund will terminate and liquidate and the Capital Protection Provider will pay the Fund any amounts due related to the Protection. This Prospectus serves as advance notice to you of any such liquidation. There are limited circumstances in which the Protection also terminates on the Termination Date, meaning the Capital Protection Provider is not obligated to pay any amounts to the Fund even where the NAV of a share class is below its Protected NAV. These circumstances are described further below under “Principal Investment Risks” as “Capital Protection Termination Risk.”

It is important to understand that the Capital Protection Agreement is a financial product that is intended to protect the Fund against significant market declines and does not in any way constitute any form of insurance. In addition, the Capital Protection Provider is not an insurance company or an insurance provider, nor is it acting as an adviser or subadviser for the Fund.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money, despite the Capital Protection Agreement. Common stocks tend to be more volatile than many other investment choices. Because the NAV per share for a share class is protected to at least 80%, and not 100%, of its highest attained NAV since the inception of the share class (as reduced to account for dividends, distributions, any extraordinary expenses, and certain extraordinary items), it is possible that in the event that equity markets fall, you could lose money, even if the Protection is triggered. In addition, if the Capital Protection Agreement does not work as intended or has been terminated, you could lose money. Because the Protected NAV is reduced by dividends, distributions, any extraordinary expenses, and certain extraordinary items, the amount of Protection could be less than 80% of the highest attained NAV for your class of shares, meaning the Protected NAV does not become a static number that only increases. To the extent that the protected amount owed to the Fund exceeds the Maximum Settlement Amount ($1.5 billion), none of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares will cover any shortfall amount, so you could lose money including amounts that would have otherwise been protected.

The Protected NAV for each share class will be posted on the Janus websites at janus.com/allfunds, or janus.com/advisor/mutual-funds for share classes other than Class D Shares. Any change to the Protected NAV is expected to be updated within one business day. Because any one share class falling below its Protected NAV can alone trigger the Protection and liquidation of the Fund, shareholders should review the Protected NAV for each share class prior to purchasing shares of this Fund, keeping in mind that each share class has different fees and expenses that impact the NAV.

Allocation Risk. Because there are risk parameters within which the portfolio manager must manage the Fund’s assets in order to maintain the Protection, the Fund’s ability to take certain investment actions that the portfolio manager might otherwise take may be limited. More specifically, complying with the provisions of the Capital Protection Agreement may impact the Fund’s allocation of assets to and within the Equity Component during the life of the Fund, may not allow the Fund to be fully invested in the Equity Component, and/or may affect the portfolio manager’s ability to respond to changing equity market conditions. This could limit the Fund’s ability to capture certain market gains when the allocations are more heavily weighted to the Protection Component. Conversely, as equity markets are rising or displaying signs of relative stability, the Fund may have more of the portfolio weighted towards assets considered to have higher risk which could increase the potential for loss of return for the Fund. Generally, the risk parameters may lead the portfolio manager to take certain investment actions that he otherwise would not take when allocating the Fund’s assets between and within the Equity Component and the Protection Component. This allocation process can have an adverse effect on the performance of the Fund, especially during periods of increased equity market volatility. The risk allocation methodology is designed so that the NAV of each share class does not fall below its Protected NAV and, if successful, protection payments are not triggered. It is possible, however, that the risk allocation methodology may not work as designed or intended and may cause the Fund to trigger the Protection, resulting in the termination of the Fund. In addition, the allocation of the Fund’s assets between and within the Equity Component and the Protection Component will likely result in a high portfolio turnover rate and additional transaction costs, such as brokerage commissions, which can impact the Fund’s returns. Because the portfolio manager allocates the Fund’s assets between and within the Equity Component and Protection Component daily according to a risk allocation methodology, there is the risk that a sudden intraday market drop may occur before the Fund’s Equity Component exposure can be reduced. Additionally, if the Fund fails to allocate its assets according to the risk allocation methodology, the Capital Protection Provider will have the option to terminate the Capital Protection Agreement, resulting in the Fund allocating 100% of its assets solely to cash and the liquidation of the Fund. Under these circumstances, the Capital Protection Provider will pay any amounts it is obligated to pay to the Fund.

Market Underperformance Risk. The Fund’s use of the risk allocation methodology and the resulting allocation between and within the Equity Component and the Protection Component may cause the Fund to underperform its primary benchmark and/or other similarly situated growth funds. This underperformance may be a result of the portfolio manager’s inability to reallocate Fund assets to respond to rising equity market conditions as quickly as another fund that invests primarily in equity securities. In addition, to maintain compliance with the risk parameters, the Fund may need to liquidate a position, or forego an investment that could have otherwise contributed to Fund performance. Under certain circumstances, the Capital Protection Agreement may require that all of the Fund’s assets be fully allocated to the Protection Component, thus limiting the upside potential for Fund returns during this period. The use of the risk allocation methodology may also impact the Fund’s performance in the event that it does not work as intended, potentially subjecting the Fund to additional expenses as a result of increased trading or allocating a larger portion of the Fund’s assets than necessary to either the Equity Component or Protection Component. Because the Fund may reallocate its assets between and within the Equity Component and the Protection Component as frequently as daily, the Fund’s reallocation will likely cause it to experience an increase in its portfolio turnover rate resulting in higher costs, which may have a negative effect on the Fund’s performance, particularly during periods of relative instability in equity markets. The Fund’s payment of the capital protection fee to the Capital Protection Provider may also result in the Fund underperforming its primary benchmark and/or other similarly situated growth funds that do not pay a protection fee.

Capital Protection Termination Risk. There is a risk that the Protection could terminate without any obligation of the Capital Protection Provider or the Parent Guarantor to make payment to the Fund. The terms and conditions of the Capital Protection Agreement are designed to protect against certain market risks inherent in any equity investment. It does not protect against certain actions or omissions that constitute gross negligence, fraud, bad faith, willful misconduct, or a criminal act on the part of the Fund, Janus Capital or certain key employees of Janus Capital, or the Fund’s custodian, that negatively impacts a share class’ NAV. Such events will result in the termination of the Protection without any obligation by the Capital Protection Provider, and therefore by the Parent Guarantor, to make any payment to the Fund. The Fund will liquidate in these events, and shareholders will not receive the Protected NAV but will instead receive the Fund’s then-current NAV at the time their shares are redeemed, which may be lower than the Protected NAV and lower than the price per share of the shareholder’s initial investment. None of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares is obligated to make any payment to the Fund or cover any shortfall. Therefore, in the event that the Protection is terminated as a result of such events, you could lose money as a result of the Fund losing the Protection under the Capital Protection Agreement, including amounts that would have otherwise been protected. This means that you could receive less than 80% of your investment and will not be reimbursed for any amounts paid under the Capital Protection Agreement.

Early Termination Events Risk. While the Capital Protection Agreement has an initial 10-year term that may be extended, there is a risk that the Capital Protection Agreement could terminate earlier under various scenarios at the option of the Capital Protection Provider, which are considered Early Termination Events. In such events, the Capital Protection Provider will be obligated to make the payment of the Settlement Amount, if due, to the Fund and the Fund will liquidate. Shareholders receive the higher of their Protected NAV or the then-current NAV for their share class, which will include any Settlement Amount due to the Fund. Examples of “Early Termination Events” include, but are not limited to (1) if the Fund, Janus Capital, or the Fund’s custodian, fails to comply with certain terms and conditions of the Capital Protection Agreement, including the failure to reallocate Fund assets when such assets fall outside the specified risk parameters, or (2) if the aggregate value of the Fund’s shares outstanding results in the Protection exceeding the Maximum Settlement Amount. The Fund is also expected to liquidate and the Capital Protection Agreement will terminate if, pursuant to the terms of the Capital Protection Agreement, the Protection is triggered. In addition, to the extent that the introduction of laws or a change of law, in each case, not known as of the date of the Capital Protection Agreement, results in a new or increased cost of capital or collateral for the Capital Protection Provider or its parent company, the Fund’s Board of Trustees will make a determination whether to approve the Fund paying such increased costs to the Capital Protection Provider or to terminate the Capital Protection Agreement. Only shareholders who hold their shares on the Termination Date are entitled to receive the Protected NAV from the Fund. Shareholders who redeem prior to the Termination Date receive the then-current NAV which will be higher than the Protected NAV for their share class and will not include any payment of the Protection.

Maximum Settlement Amount Risk. The Capital Protection Agreement currently covers the outstanding shares of each class of shares offered by the Fund having an aggregate protected amount up to an initial value of $1.5 billion. If the Maximum Settlement Amount exceeds $1.5 billion without any additional coverage being extended to the Fund, the Capital Protection Provider will not be liable for any Settlement Amount payment in excess of $1.5 billion. None of the Fund, Janus Capital, any affiliate thereof, or any company offering the shares will be responsible for any portion of the Settlement Amount, including any amounts which may exceed the Maximum Settlement Amount. Therefore, although the Protection applies, you could lose money to the extent the Aggregate Shortfall Amount exceeds the Maximum Settlement Amount including amounts that would have otherwise been protected. This means that you could receive less than 80% of your investment. In any event, as the Fund’s assets grow, the Fund intends to take such actions as may be deemed necessary, including limiting shareholder purchases, to limit the Aggregate Shortfall Amount to a level so that it does not exceed the Maximum Settlement Amount, but there is no guarantee that such efforts will be successful. There is no guarantee that the Capital Protection Provider will agree to extend coverage beyond $1.5 billion.

Liquidation Risk. Although the risk allocation methodology is designed so that the NAV of each share class does not fall below its Protected NAV, there is the possibility that the risk allocation methodology may not work as designed or redemptions, particularly a large redemption, may impact the allocation process, and the NAV of any share class falls below its Protected NAV. If this happens, it is expected that the Fund will receive payment of the Settlement Amount from the Capital Protection Provider, if due, and liquidate as soon as possible following the event. The NAV of one share class falling below its Protected NAV will result in the Protection being triggered and, as a result, the liquidation of the entire Fund, even though the NAV of one or more other share classes remains at or above its Protected NAV. Other events described in this Prospectus may, at the discretion of the Fund or Capital Protection Provider, as applicable, also terminate the Capital Protection Agreement resulting in payment of the Settlement Amount and liquidation of the Fund. In the event the Protection is triggered and the Fund begins the liquidation process, no other purchases will be permitted, and the payment of redemption proceeds will be suspended, likely from the day the Protection is triggered; shareholders receive the higher of their Protected NAV or the then-current NAV for their share class, which will include any Settlement Amount due to the Fund. Redemptions are taxable events. This Prospectus serves as advance notice to shareholders of any rejection of purchases, suspension of the payment of redemption proceeds, and liquidation of the Fund. In the event that the Capital Protection Agreement is terminated and the Fund begins the liquidation process, Janus Capital will make such information available at janus.com/allfunds, or janus.com/advisor/mutual-funds for share classes other than Class D Shares. Notice of the Fund liquidation will otherwise be made when you receive your redemption proceeds. For illustrative purposes to understand a scenario where the Protection is triggered and the Fund proceeds to liquidation, see below:

Protected NAV across all share classes is $10.00 –

• Day 1 (Tuesday) – One share class NAV is $9.00 and each other share class’ NAV is $11.00. Purchases are rejected and the payment of redemptions is suspended as the Fund proceeds to liquidation since there is at least one share class’ NAV that is below its Protected NAV.

• Day 7 (Monday) – Fund receives Protection payment from the Capital Protection Provider, and the Fund liquidates and terminates and pays out a $10.00 Protected NAV to the share class that had a $9.00 NAV. All other share classes are redeemed at $11.00 NAV, plus the Settlement Amount distributed pro rata to their share class.

Opportunity Cost Risk. It is possible that under the terms of the Capital Protection Agreement, the Fund’s allocation to the Equity Component could drop to a low level or be eliminated altogether, especially during periods of heightened volatility in equity markets. This would reduce the Fund’s ability to participate in upward equity market movements, and therefore, represents loss of opportunity compared to a fund that is fully invested in equity securities.

Counterparty Risk (Capital Protection Provider and its Parent Company). A shareholder’s ability to receive the Protected NAV from the Fund is dependent on the Fund’s ability to collect the Settlement Amount from the Capital Protection Provider pursuant to the terms of the Capital Protection Agreement or from the Capital Protection Provider’s parent under a separate parent guaranty. Fund transactions involving a counterparty, such as the Capital Protection Provider, are subject to the risk that the counterparty or a third party will not fulfill its obligation to the Fund (“counterparty risk”). Counterparty risk may arise because of the counterparty’s financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. As such, the Fund’s ability to benefit from the Protection may depend on the Capital Protection Provider’s, as well as its parent company’s, financial condition. As an added measure of protection, BNP Paribas, the parent company of the Capital Protection Provider, has issued an absolute, irrevocable and continuing guaranty pursuant to which it guarantees any and all financial obligations of the Capital Protection Provider under the Capital Protection Agreement. There is, however, a risk that the Capital Protection Provider’s parent company may not fulfill its obligations under the guaranty it has issued.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The Fund’s use of the risk allocation methodology is intended to protect against significant downward movement of the NAV per share for a share class, particularly in times of heightened volatility in the equity markets, but the methodology may not protect the Fund if equity markets take a sudden and/or significant fall.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio manager’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s return. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Derivatives Risk. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations to the Fund. If the counterparty to a derivative transaction defaults, such as the Capital Protection Provider or Parent Guarantor, the Fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund enters into short derivative positions, the Fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s losses are theoretically unlimited.

Foreign Exposure Risk. The Fund may have exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks.

Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders. The risk allocation methodology utilized by the Fund will likely increase the level of portfolio turnover.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money, despite the Capital Protection Agreement.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The Fund does not have a full calendar year of operations. Performance information for certain periods is included in the Fund’s first annual and/or semiannual report.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess The Fund does not have a full calendar year of operations.
Janus Protected Series - Growth | Class D Shares | Class D
  
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.64%
Other Expenses rr_OtherExpensesOverAssets 3.00%
Capital Protection Fee rr_Component3OtherExpensesOverAssets 0.75%
Remaining Other Expenses rr_Component2OtherExpensesOverAssets 2.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 3.64% [12]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 1.86% [12]
Net Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.78% [12]
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 366
3 Years rr_ExpenseExampleYear03 1,114
5 Years rr_ExpenseExampleYear05 1,883
10 Years rr_ExpenseExampleYear10 3,897
Perkins Global Value Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Perkins Global Value Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Perkins Global Value Fund seeks capital appreciation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund.
Expense Breakpoint Discounts jif277751_ExpenseBreakpointDiscountsAbstract  
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 26 of the Fund’s Prospectus and in the “Purchases” section on page 90 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 51% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 51.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks of companies of any size located throughout the world, including emerging markets. The Fund normally invests in issuers from several different countries, which may include the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign equity and debt securities.

The Fund focuses on companies that have fallen out of favor with the market or that appear to be temporarily misunderstood by the investment community. The Fund’s portfolio manager generally looks for companies with:

• strong balance sheets and solid recurring free cash flows

• attractive relative and absolute valuation ratios or that have underperformed recently

• favorable reward to risk characteristics

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.

Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. As of September 30, 2011, approximately 4.5% of the Fund’s investments were in emerging markets.

Value Investing Risk. Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “value” stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class T Shares (formerly named Class J Shares, the initial share class) of the Fund commenced operations with the Fund’s inception. Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund commenced operations on July 6, 2009.

• The performance shown for Class T Shares is calculated using the fees and expenses of Class T Shares in effect during the periods shown, net of any applicable fee and expense limitations or waivers.

• The performance shown for Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of each respective share class, without the effect of any fee and expense limitations or waivers.

• The performance shown for Class I Shares for periods prior to July 6, 2009, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses of Class J Shares, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class S Shares, and Class I Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown for each respective share class may have been different. The performance shown for periods following the Fund’s commencement of Class A Shares, Class C Shares, Class S Shares, and Class I Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.07%          Worst Quarter: Third Quarter 2002 -21.31%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using distributions for the Fund’s Class T Shares (formerly named Class J Shares, the initial share class). After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are only shown for Class T Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class T Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Perkins Global Value Fund | Class A, C, S, I, T Shares | Class A
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class A
Management Fees rr_ManagementFeesOverAssets 0.61%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.42%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.28%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class A Shares
1 Year rr_ExpenseExampleYear01 698
3 Years rr_ExpenseExampleYear03 958
5 Years rr_ExpenseExampleYear05 1,237
10 Years rr_ExpenseExampleYear10 2,031
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 698
3 Years rr_ExpenseExampleNoRedemptionYear03 958
5 Years rr_ExpenseExampleNoRedemptionYear05 1,237
10 Years rr_ExpenseExampleNoRedemptionYear10 2,031
Perkins Global Value Fund | Class A, C, S, I, T Shares | Class C
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class C
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption none
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class C
Management Fees rr_ManagementFeesOverAssets 0.61%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.30%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.91%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class C Shares
1 Year rr_ExpenseExampleYear01 294
3 Years rr_ExpenseExampleYear03 600
5 Years rr_ExpenseExampleYear05 1,032
10 Years rr_ExpenseExampleYear10 2,233
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 194
3 Years rr_ExpenseExampleNoRedemptionYear03 600
5 Years rr_ExpenseExampleNoRedemptionYear05 1,032
10 Years rr_ExpenseExampleNoRedemptionYear10 2,233
Perkins Global Value Fund | Class A, C, S, I, T Shares | Class S
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class S
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class S
Management Fees rr_ManagementFeesOverAssets 0.61%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.51%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.37%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class S Shares
1 Year rr_ExpenseExampleYear01 139
3 Years rr_ExpenseExampleYear03 434
5 Years rr_ExpenseExampleYear05 750
10 Years rr_ExpenseExampleYear10 1,646
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 139
3 Years rr_ExpenseExampleNoRedemptionYear03 434
5 Years rr_ExpenseExampleNoRedemptionYear05 750
10 Years rr_ExpenseExampleNoRedemptionYear10 1,646
Perkins Global Value Fund | Class A, C, S, I, T Shares | Class I
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class I
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class I
Management Fees rr_ManagementFeesOverAssets 0.61%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.92%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class I Shares
1 Year rr_ExpenseExampleYear01 94
3 Years rr_ExpenseExampleYear03 293
5 Years rr_ExpenseExampleYear05 509
10 Years rr_ExpenseExampleYear10 1,131
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 94
3 Years rr_ExpenseExampleNoRedemptionYear03 293
5 Years rr_ExpenseExampleNoRedemptionYear05 509
10 Years rr_ExpenseExampleNoRedemptionYear10 1,131
Perkins Global Value Fund | Class A, C, S, I, T Shares | Class T
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class T
Management Fees rr_ManagementFeesOverAssets 0.61%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.10%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class T Shares
1 Year rr_ExpenseExampleYear01 112
3 Years rr_ExpenseExampleYear03 350
5 Years rr_ExpenseExampleYear05 606
10 Years rr_ExpenseExampleYear10 1,340
Expense Example, No Redemption: rr_ExpenseExampleNoRedemptionAbstract  
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 112
3 Years rr_ExpenseExampleNoRedemptionYear03 350
5 Years rr_ExpenseExampleNoRedemptionYear05 606
10 Years rr_ExpenseExampleNoRedemptionYear10 1,340
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (15.91%)
2003 rr_AnnualReturn2003 38.41%
2004 rr_AnnualReturn2004 15.33%
2005 rr_AnnualReturn2005 4.07%
2006 rr_AnnualReturn2006 11.19%
2007 rr_AnnualReturn2007 12.10%
2008 rr_AnnualReturn2008 (37.83%)
2009 rr_AnnualReturn2009 31.96%
2010 rr_AnnualReturn2010 11.23%
2011 rr_AnnualReturn2011 1.70%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2002
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.31%)
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class A
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class A Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 (4.36%)
5 Years rr_AverageAnnualReturnYear05 (0.56%)
10 Years rr_AverageAnnualReturnYear10 4.07%
Since Inception rr_AverageAnnualReturnSinceInception 4.56%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class C
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class C Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 (0.09%)
5 Years rr_AverageAnnualReturnYear05 (0.06%)
10 Years rr_AverageAnnualReturnYear10 3.95%
Since Inception rr_AverageAnnualReturnSinceInception 4.42%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class S
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class S Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.52%
5 Years rr_AverageAnnualReturnYear05 0.65%
10 Years rr_AverageAnnualReturnYear10 4.63%
Since Inception rr_AverageAnnualReturnSinceInception 5.10%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class I
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class I Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.91%
5 Years rr_AverageAnnualReturnYear05 0.70%
10 Years rr_AverageAnnualReturnYear10 4.86%
Since Inception rr_AverageAnnualReturnSinceInception 5.33%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return Before Taxes | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.70%
5 Years rr_AverageAnnualReturnYear05 0.79%
10 Years rr_AverageAnnualReturnYear10 4.92%
Since Inception rr_AverageAnnualReturnSinceInception 5.38%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.85%
5 Years rr_AverageAnnualReturnYear05 0.05%
10 Years rr_AverageAnnualReturnYear10 4.30%
Since Inception rr_AverageAnnualReturnSinceInception 4.78%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class T Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.22%
5 Years rr_AverageAnnualReturnYear05 0.52%
10 Years rr_AverageAnnualReturnYear10 4.22%
Since Inception rr_AverageAnnualReturnSinceInception 4.64%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 3.34%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class A, C, S, I, T Shares | Morgan Stanley Capital International World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.54%)
5 Years rr_AverageAnnualReturnYear05 (2.37%)
10 Years rr_AverageAnnualReturnYear10 3.62%
Since Inception rr_AverageAnnualReturnSinceInception 2.73%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class D Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY Perkins Global Value Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Perkins Global Value Fund seeks capital appreciation.
FEES AND EXPENSES OF THE FUND jif277751_FundFeesAndExpensesAbstract  
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES (fees paid directly from your investment)
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by Year [Heading] rr_ExpenseExampleByYearHeading The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover: jif277751_PortfolioTurnoverAltAbstract  
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover:
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 51% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 51.00%
Principal Investment Strategies jif277751_PrincipalInvestmentStrategiesAbstract  
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment objective by investing primarily in common stocks of companies of any size located throughout the world, including emerging markets. The Fund normally invests in issuers from several different countries, which may include the United States. The Fund may, under unusual circumstances, invest in a single country. The Fund may have significant exposure to emerging markets. The Fund may also invest in U.S. and foreign equity and debt securities.

The Fund focuses on companies that have fallen out of favor with the market or that appear to be temporarily misunderstood by the investment community. The Fund’s portfolio manager generally looks for companies with:

• strong balance sheets and solid recurring free cash flows

• attractive relative and absolute valuation ratios or that have underperformed recently

• favorable reward to risk characteristics

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to 1/3 of its total assets as determined at the time of the loan origination.
Principal Investment Risks jif277751_PrincipalInvestmentRisksAbstract  
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. As of September 30, 2011, approximately 4.5% of the Fund’s investments were in emerging markets.

Value Investing Risk. Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “value” stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
PERFORMANCE INFORMATION jif277751_FundPastPerformanceAbstract  
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time.

The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/allfunds
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-525-3713
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class D Shares (calendar year-end)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter: Second Quarter 2009 26.07%          Worst Quarter: Third Quarter 2002 -21.31%
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (periods ended 12/31/11)
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following February 16, 2010; and for the Fund’s Class J Shares, the predecessor share class, for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.
Perkins Global Value Fund | Class D Shares | Class D
  
SHAREHOLDER FEES rr_ShareholderFeesAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName Class D
Redemption fee on Shares held for 90 days or less (as a percentage of amount redeemed) Effective April 2, 2012, the Fund will no longer assess a redemption fee on Shares, regardless of how long such Shares have been held. rr_RedemptionFeeOverRedemption 2.00%
ANNUAL FUND OPERATING EXPENSES rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Class D
Management Fees rr_ManagementFeesOverAssets 0.61%
Other Expenses rr_OtherExpensesOverAssets 0.43%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.04%
EXAMPLE: rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Class D Shares
1 Year rr_ExpenseExampleYear01 106
3 Years rr_ExpenseExampleYear03 331
5 Years rr_ExpenseExampleYear05 574
10 Years rr_ExpenseExampleYear10 1,271
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 (15.91%)
2003 rr_AnnualReturn2003 38.41%
2004 rr_AnnualReturn2004 15.33%
2005 rr_AnnualReturn2005 4.07%
2006 rr_AnnualReturn2006 11.19%
2007 rr_AnnualReturn2007 12.10%
2008 rr_AnnualReturn2008 (37.83%)
2009 rr_AnnualReturn2009 31.96%
2010 rr_AnnualReturn2010 11.45%
2011 rr_AnnualReturn2011 1.75%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 26.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2002
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.31%)
Perkins Global Value Fund | Class D Shares | Return Before Taxes | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.75%
5 Years rr_AverageAnnualReturnYear05 0.84%
10 Years rr_AverageAnnualReturnYear10 4.94%
Since Inception rr_AverageAnnualReturnSinceInception 5.40%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class D Shares | Return After Taxes on Distributions | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.89%
5 Years rr_AverageAnnualReturnYear05 0.09%
10 Years rr_AverageAnnualReturnYear10 4.32%
Since Inception rr_AverageAnnualReturnSinceInception 4.80%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Class D Shares
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares [3]
1 Year rr_AverageAnnualReturnYear01 2.26%
5 Years rr_AverageAnnualReturnYear05 0.56%
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 4.66%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class D Shares | Morgan Stanley Capital International All Country World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International All Country World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.35%)
5 Years rr_AverageAnnualReturnYear05 (1.93%)
10 Years rr_AverageAnnualReturnYear10 4.24%
Since Inception rr_AverageAnnualReturnSinceInception 3.34%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
Perkins Global Value Fund | Class D Shares | Morgan Stanley Capital International World Index℠ (net)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Morgan Stanley Capital International World IndexSM (net)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for expenses, fees, or taxes)
1 Year rr_AverageAnnualReturnYear01 (5.54%)
5 Years rr_AverageAnnualReturnYear05 (2.37%)
10 Years rr_AverageAnnualReturnYear10 3.62%
Since Inception rr_AverageAnnualReturnSinceInception 2.73%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2001
[1] Calculated assuming maximum permitted sales loads.
[2] The one year return is calculated to include the contingent deferred sales charge.
[3] If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund's other return figures.
[4] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding any performance adjustments to management fees, the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, Class S Shares, and Class R Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 0.78% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[5] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, Class S Shares, and Class R Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 0.70% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[6] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, and Class S Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 1.05% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[7] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, Class S Shares, and Class R Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 1.75% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[8] Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.
[9] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding any performance adjustments to management fees, the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, and Class S Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 1.25% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[10] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding any performance adjustments to management fees, administrative services fees payable pursuant to the Transfer Agency Agreement, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) to 1.25% until at least February 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.
[11] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, and Class S Shares; administrative services fees payable pursuant to the Transfer Agency Agreement (except for networking and omnibus fees); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to between 1.38% and 1.53%, depending on the amount of the capital protection fee. The contractual waiver may be terminated or modified prior to February 1, 2013 only at the discretion of the Fund's Board of Trustees.
[12] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the administrative services fees payable pursuant to the Transfer Agency Agreement, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) to between 1.38% and 1.53%, depending on the amount of the capital protection fee. The contractual waiver may be terminated or modified prior to February 1, 2013 only at the discretion of the Fund's Board of Trustees.