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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName JANUS INVESTMENT FUND
Prospectus Date rr_ProspectusDate Oct. 26, 2012
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund summary

Janus Flexible Bond Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Flexible Bond Fund seeks to obtain maximum total return, consistent with preservation of capital.
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.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES
(fees paid directly from your investment)
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)
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 126% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 126.00%
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 51 of the Fund’s Prospectus and in the “Purchases” section on page 83 of the Fund’s Statement of Additional Information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE:
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 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, Caption [Text] rr_ExpenseExampleByYearCaption If Shares are redeemed:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If Shares are not redeemed:
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock The Fund pursues its investment objective by primarily investing, under normal circumstances, at least 80% of its net assets in bonds. Bonds include, but are not limited to, government notes and bonds, corporate bonds, convertible bonds, mortgage-backed securities, and zero-coupon bonds. The Fund will invest at least 65% of its assets in investment grade debt securities. As of June 30, 2012, the Fund’s weighted average maturity was 7.9 years. The Fund will limit its investment in high-yield/high-risk bonds, also known as “junk bonds,” to 35% or less of its net assets. The Fund generates total return from a combination of current income and capital appreciation, but income is usually the dominant portion. The Fund may also invest in asset-backed securities, money market instruments, bank loans, and foreign debt securities (which may include investments in emerging markets). Due to the nature of the securities in which the Fund invests, it may have relatively high portfolio turnover compared to other Funds.

In addition, 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. In particular, the Fund may use interest rate futures to manage portfolio risk. The Fund’s exposure to derivatives will vary. For purposes of meeting its 80% investment policy, the Fund may include derivatives that have characteristics similar to the Fund’s direct investments. 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 addition to considering economic factors such as the effect of interest rates on the Fund’s investments, the portfolio managers apply a “bottom up” approach in choosing investments. This means that the portfolio managers look at income-producing securities one at a time to determine if a security is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.
Risk [Heading] rr_RiskHeading PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock Although the Fund may be less volatile than funds that invest most of their assets in common stocks, the Fund’s returns and yields will vary, and you could lose money.

Fixed-Income Securities Risk. The Fund invests in a variety of fixed-income securities. 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. Credit risk is the risk that the credit strength of an issuer of a fixed-income security will weaken and/or that the issuer will be unable to make timely principal and interest payments and that the security may go into default. Prepayment risk is the risk that during periods of falling interest rates, certain fixed-income securities with higher interest rates, such as mortgage- and asset-backed securities, may be prepaid by their issuers thereby reducing the amount of interest payments. Valuation risk is the risk that one or more of the fixed-income securities in which the Fund invests are priced incorrectly due to factors such as incomplete data, market instability, or human error. Liquidity risk is the risk that fixed-income securities may be difficult or impossible to sell at the time that the Fund would like or at the price that the portfolio managers believe the security is currently worth.

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.

Sovereign Debt Risk. The Fund may invest in U.S. and foreign government debt securities (“sovereign debt”). Investments in U.S. sovereign debt are considered low risk. However, investments in non-U.S. sovereign debt can involve a high degree of risk, including the risk that the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or to pay the interest on its sovereign debt in a timely manner.

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.

Bank Loan Risk. Bank loans are obligations of companies or other entities entered into in connection with recapitalizations, acquisitions, and refinancings. The Fund’s investments in bank loans are generally acquired as a participation interest in, or assignment of, loans originated by a lender or other financial institution. These investments may include institutionally-traded floating and fixed-rate debt securities. Participation interests and assignments involve credit, interest rate, and liquidity risk. In addition, the bank loans underlying these securities often involve borrowers with low credit ratings whose financial conditions are troubled or uncertain, including companies that are highly leveraged or in bankruptcy proceedings.

Foreign Exposure Risk. The Fund may have exposure to foreign markets as a result of its investments in foreign securities, including investments in 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. To the extent the Fund invests in foreign debt securities, such investments are sensitive to changes in interest rates. Additionally, investments in securities of foreign governments involve the risk that a foreign government may not be willing or able to pay interest or repay principal when due. 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.

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.

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.

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 Although the Fund may be less volatile than funds that invest most of their assets in common stocks, the Fund’s returns and yields 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.
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. Class N Shares of the Fund commenced operations on May 31, 2012.
  • 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, net of any applicable fee and expense limitations or waivers.
  • The performance shown for Class N Shares for periods prior to December 31, 2011, reflects the performance of the Fund’s Class T Shares, calculated using the fees and expenses of Class T Shares, net of any applicable 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, or Class N Shares of the Fund had been available during periods prior to December 31, 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, Class I Shares, Class N 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.
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 Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-877-335-2687
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress janus.com/advisor/mutual-funds
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.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns for Class T Shares (calendar year-end)
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.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter:  Third Quarter 2009  5.58%          Worst Quarter:  Second Quarter 2004  −2.99%
Year to Date Return, Label rr_YearToDateReturnLabel The Fund’s year-to-date return as of the calendar quarter ended September 30, 2012 was 7.11%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12/31/11)
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.
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 Closing [Text Block] rr_PerformanceTableClosingTextBlock Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class A
  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName
Class A
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class A
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.11%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.77%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class A Shares
1 Year rr_ExpenseExampleYear01 550
3 Years rr_ExpenseExampleYear03 709
5 Years rr_ExpenseExampleYear05 883
10 Years rr_ExpenseExampleYear10 1,384
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 550
3 Years rr_ExpenseExampleNoRedemptionYear03 709
5 Years rr_ExpenseExampleNoRedemptionYear05 883
10 Years rr_ExpenseExampleNoRedemptionYear10 1,384
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class C
  
Risk/Return: rr_RiskReturnAbstract  
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%
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class C
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.55%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class C Shares
1 Year rr_ExpenseExampleYear01 258
3 Years rr_ExpenseExampleYear03 490
5 Years rr_ExpenseExampleYear05 845
10 Years rr_ExpenseExampleYear10 1,845
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 158
3 Years rr_ExpenseExampleNoRedemptionYear03 490
5 Years rr_ExpenseExampleNoRedemptionYear05 845
10 Years rr_ExpenseExampleNoRedemptionYear10 1,845
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class S
  
Risk/Return: rr_RiskReturnAbstract  
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
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class S
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.95%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class S Shares
1 Year rr_ExpenseExampleYear01 97
3 Years rr_ExpenseExampleYear03 303
5 Years rr_ExpenseExampleYear05 525
10 Years rr_ExpenseExampleYear10 1,166
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 97
3 Years rr_ExpenseExampleNoRedemptionYear03 303
5 Years rr_ExpenseExampleNoRedemptionYear05 525
10 Years rr_ExpenseExampleNoRedemptionYear10 1,166
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class I
  
Risk/Return: rr_RiskReturnAbstract  
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
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class I
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.14%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.55%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class I Shares
1 Year rr_ExpenseExampleYear01 56
3 Years rr_ExpenseExampleYear03 176
5 Years rr_ExpenseExampleYear05 307
10 Years rr_ExpenseExampleYear10 689
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 56
3 Years rr_ExpenseExampleNoRedemptionYear03 176
5 Years rr_ExpenseExampleNoRedemptionYear05 307
10 Years rr_ExpenseExampleNoRedemptionYear10 689
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class N
  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees Column [Text] rr_ShareholderFeesColumnName
Class N
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
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class N
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.05% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.46%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class N Shares
1 Year rr_ExpenseExampleYear01 47
3 Years rr_ExpenseExampleYear03 148
5 Years rr_ExpenseExampleYear05 258
10 Years rr_ExpenseExampleYear10 579
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class N Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 47
3 Years rr_ExpenseExampleNoRedemptionYear03 148
5 Years rr_ExpenseExampleNoRedemptionYear05 258
10 Years rr_ExpenseExampleNoRedemptionYear10 579
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class R
  
Risk/Return: rr_RiskReturnAbstract  
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
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class R
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.20%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class R Shares
1 Year rr_ExpenseExampleYear01 122
3 Years rr_ExpenseExampleYear03 381
5 Years rr_ExpenseExampleYear05 660
10 Years rr_ExpenseExampleYear10 1,455
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class R Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 122
3 Years rr_ExpenseExampleNoRedemptionYear03 381
5 Years rr_ExpenseExampleNoRedemptionYear05 660
10 Years rr_ExpenseExampleNoRedemptionYear10 1,455
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Class T
  
Risk/Return: rr_RiskReturnAbstract  
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
Operating Expenses Column [Text] rr_OperatingExpensesColumnName
Class T
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.70%
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class T Shares
1 Year rr_ExpenseExampleYear01 72
3 Years rr_ExpenseExampleYear03 224
5 Years rr_ExpenseExampleYear05 390
10 Years rr_ExpenseExampleYear10 871
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 72
3 Years rr_ExpenseExampleNoRedemptionYear03 224
5 Years rr_ExpenseExampleNoRedemptionYear05 390
10 Years rr_ExpenseExampleNoRedemptionYear10 871
2002 rr_AnnualReturn2002 9.93%
2003 rr_AnnualReturn2003 6.37%
2004 rr_AnnualReturn2004 3.82%
2005 rr_AnnualReturn2005 1.79%
2006 rr_AnnualReturn2006 4.12%
2007 rr_AnnualReturn2007 6.87%
2008 rr_AnnualReturn2008 5.64%
2009 rr_AnnualReturn2009 12.54%
2010 rr_AnnualReturn2010 7.45%
2011 rr_AnnualReturn2011 6.50%
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2012
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 7.11%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.58%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2004
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.99%)
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class A
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class A Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
 [2]
1 Year rr_AverageAnnualReturnYear01 1.38%
5 Years rr_AverageAnnualReturnYear05 6.68%
10 Years rr_AverageAnnualReturnYear10 5.92%
Since Inception rr_AverageAnnualReturnSinceInception 7.31%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class C
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class C Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
 [3]
1 Year rr_AverageAnnualReturnYear01 4.63%
5 Years rr_AverageAnnualReturnYear05 6.98%
10 Years rr_AverageAnnualReturnYear10 5.73%
Since Inception rr_AverageAnnualReturnSinceInception 6.85%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class S
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class S Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.24%
5 Years rr_AverageAnnualReturnYear05 7.54%
10 Years rr_AverageAnnualReturnYear10 6.24%
Since Inception rr_AverageAnnualReturnSinceInception 7.38%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class I
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class I Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.66%
5 Years rr_AverageAnnualReturnYear05 7.77%
10 Years rr_AverageAnnualReturnYear10 6.46%
Since Inception rr_AverageAnnualReturnSinceInception 7.54%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class N
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class N Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.50%
5 Years rr_AverageAnnualReturnYear05 7.77%
10 Years rr_AverageAnnualReturnYear10 6.46%
Since Inception rr_AverageAnnualReturnSinceInception 7.54%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class R
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class R Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.98%
5 Years rr_AverageAnnualReturnYear05 7.27%
10 Years rr_AverageAnnualReturnYear10 5.99%
Since Inception rr_AverageAnnualReturnSinceInception 7.12%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return Before Taxes | Class T
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class T Shares
Label rr_AverageAnnualReturnLabel
Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.50%
5 Years rr_AverageAnnualReturnYear05 7.77%
10 Years rr_AverageAnnualReturnYear10 6.46%
Since Inception rr_AverageAnnualReturnSinceInception 7.54%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return After Taxes on Distributions | Class T
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class T Shares
Label rr_AverageAnnualReturnLabel
Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 4.88%
5 Years rr_AverageAnnualReturnYear05 5.92%
10 Years rr_AverageAnnualReturnYear10 4.67%
Since Inception rr_AverageAnnualReturnSinceInception 4.92%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class T
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName
Class T Shares
Label rr_AverageAnnualReturnLabel
Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 4.44%
5 Years rr_AverageAnnualReturnYear05 5.61%
10 Years rr_AverageAnnualReturnYear10 4.50%
Since Inception rr_AverageAnnualReturnSinceInception 4.87%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
Janus Flexible Bond Fund | Class A, C, S, I, N, R, T Shares | Barclays U.S. Aggregate Bond Index (reflects no deduction for expenses, fees, or taxes)
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel
Barclays U.S. Aggregate Bond Index
1 Year rr_AverageAnnualReturnYear01 7.84%
5 Years rr_AverageAnnualReturnYear05 6.50%
10 Years rr_AverageAnnualReturnYear10 5.78%
Since Inception rr_AverageAnnualReturnSinceInception 7.34%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 07, 1987
[1] Other Expenses for Class N Shares are based on the estimated expenses that the Shares expect to incur during their initial fiscal period.
[2] Calculated assuming maximum permitted sales loads.
[3] The one year return is calculated to include the contingent deferred sales charge.