Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

JANUS INVESTMENT FUND

Prospectus Date

rr_ProspectusDate

Jan. 28, 2015

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

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FUND SUMMARY

Janus Emerging Markets Fund

Objective [Heading]

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INVESTMENT OBJECTIVE

Objective, Primary [Text Block]

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Janus Emerging Markets Fund seeks long-term growth of capital.

Expense [Heading]

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FEES AND EXPENSES OF THE FUND

Expense Narrative [Text Block]

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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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 1, 2016

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 59% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

59.00%

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 83 of the Fund’s Prospectus and in the “Purchases” section on page 82 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 without waivers 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 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, 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 investing, 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 MSCI World Index^SM, 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 that are economically tied to emerging market countries, it may invest up to 20% of its net assets in securities of issuers that are economically tied to 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 invest 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, mortgage-backed securities, real estate-backed securities, securities of real estate investment trusts (“REITs”) and similar REIT-like entities. A REIT is a trust that invests in real estate-related projects, such as properties, mortgage loans, and construction loans. REITs are generally categorized as equity, mortgage, or hybrid REITs. A REIT may be listed on an exchange or traded over-the-counter.

The Fund may also take long or short positions in derivatives, which are instruments that have a value derived from, or directly linked to, an underlying asset, such as equity securities, fixed-income securities, commodities, currencies, interest rates, or market indices. For purposes of meeting its 80% investment policy, the Fund may include derivatives that have characteristics similar to the securities in which the Fund may directly invest. The types of derivatives in which the Fund may invest include options, futures, swaps, warrants, and forward exchange contracts. The Fund may use derivatives to hedge, to earn income or enhance returns, as a substitute for securities in which the Fund invests, to increase or decrease the Fund’s exposure to a particular market, to adjust the Fund’s currency exposure relative to its benchmark index, to gain access to foreign markets where direct investment may be restricted or unavailable, or to manage the Fund’s risk profile.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.

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 as a result of its investments in foreign securities, particularly 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.

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, imposition or enforcement of foreign ownership limits, seizure, nationalization, sanctions or imposition of restrictions by various governmental entities on investment and trading, 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. Additionally, foreign and emerging market risks, including but not limited to price controls, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, nationalization, and restrictions on repatriation of assets may be heightened to the extent the Fund invests in Chinese local market securities (also known as “A Shares”). 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 other 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. Market risk may affect a single issuer, industry, economic sector, or the market as a whole.

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 returns. 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 investment can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Leverage may cause the Fund to be more volatile than if it had not used 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.

Real Estate Securities Risk. The Fund’s performance may be affected by the risks associated with investments in real estate-related companies. The value of real estate-related companies’ securities 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 company. Investments in REITs involve the same risks as other real estate investments. In addition, a REIT could fail to qualify for tax-free pass-through of its income under the Internal Revenue Code or fail to maintain its exemption from registration under the Investment Company Act of 1940, as amended, which could produce adverse economic consequences for the REIT and its investors, including the Fund.

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. Accordingly, there may be times when an ETF trades at a premium or discount. 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 securities in which the ETF is invested, 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.

Management Risk. The Fund is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies employed for the Fund may fail to produce the intended results. The Fund may underperform its benchmark index or other mutual funds with similar investment objectives.

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.

Bar Chart and Performance Table [Heading]

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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 A Shares, Class C Shares, Class S Shares, Class I Shares, and Class T Shares of the Fund commenced operations with the Fund’s inception.

• The performance shown for Class A Shares, Class C Shares, Class S Shares, Class I Shares, and Class T Shares is calculated using the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.
• The performance shown for Class N Shares reflects the performance of the Fund’s Class I Shares, calculated using the fees and expenses of Class N Shares, without the effect of any fee and expense limitations or waivers. If Class N Shares of the Fund had been available during the periods shown, the performance may have been different.

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 I 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:  1st Quarter 2012  16.05%          Worst Quarter:  3rd Quarter 2011  −24.70%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (periods ended 12/31/14)

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.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

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.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The MSCI Emerging Markets Index^SM is a free float-adjusted market capitalization index that is designed to measure equity market performance of emerging markets. The index includes reinvestment of dividends, net of foreign withholding taxes. This index is used to calculate the performance fee adjustment.

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 Closing [Text Block]

rr_PerformanceTableClosingTextBlock

Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.

Janus Emerging Markets Fund | Class A, C, S, I, N, 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

5.75%

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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.82%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.97%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.50%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

1.47%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class A Shares

1 Year

rr_ExpenseExampleYear01

763

3 Years

rr_ExpenseExampleYear03

1,158

5 Years

rr_ExpenseExampleYear05

1,576

10 Years

rr_ExpenseExampleYear10

2,739

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class A Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

763

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,158

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,576

10 Years

rr_ExpenseExampleNoRedemptionYear10

2,739

Janus Emerging Markets Fund | Class A, C, S, I, N, 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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.78%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.68%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.55%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

2.13%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class C Shares

1 Year

rr_ExpenseExampleYear01

371

3 Years

rr_ExpenseExampleYear03

832

5 Years

rr_ExpenseExampleYear05

1,420

10 Years

rr_ExpenseExampleYear10

3,012

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class C Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

271

3 Years

rr_ExpenseExampleNoRedemptionYear03

832

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,420

10 Years

rr_ExpenseExampleNoRedemptionYear10

3,012

Janus Emerging Markets Fund | Class A, C, S, I, N, 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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.90%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.05%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.53%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

1.52%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class S Shares

1 Year

rr_ExpenseExampleYear01

208

3 Years

rr_ExpenseExampleYear03

643

5 Years

rr_ExpenseExampleYear05

1,103

10 Years

rr_ExpenseExampleYear10

2,379

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class S Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

208

3 Years

rr_ExpenseExampleNoRedemptionYear03

643

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,103

10 Years

rr_ExpenseExampleNoRedemptionYear10

2,379

Janus Emerging Markets Fund | Class A, C, S, I, N, 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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.62%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.52%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.51%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

1.01%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class I Shares

1 Year

rr_ExpenseExampleYear01

155

3 Years

rr_ExpenseExampleYear03

480

5 Years

rr_ExpenseExampleYear05

829

10 Years

rr_ExpenseExampleYear10

1,813

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class I Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

155

3 Years

rr_ExpenseExampleNoRedemptionYear03

480

5 Years

rr_ExpenseExampleNoRedemptionYear05

829

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,813

2011

rr_AnnualReturn2011

(24.02%)

2012

rr_AnnualReturn2012

14.40%

2013

rr_AnnualReturn2013

(0.25%)

2014

rr_AnnualReturn2014

(0.12%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.05%

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, N, 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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.62%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.52%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.51%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

1.01%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class N Shares

1 Year

rr_ExpenseExampleYear01

155

3 Years

rr_ExpenseExampleYear03

480

5 Years

rr_ExpenseExampleYear05

829

10 Years

rr_ExpenseExampleYear10

1,813

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class N Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

155

3 Years

rr_ExpenseExampleNoRedemptionYear03

480

5 Years

rr_ExpenseExampleNoRedemptionYear05

829

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,813

Janus Emerging Markets Fund | Class A, C, S, I, N, 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 (may adjust up or down)

rr_ManagementFeesOverAssets

0.90%

Distribution/Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.87%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.77%

^[1]

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

0.50%

^[1]

Total Annual Fund Operating Expenses After Fee Waiver

rr_NetExpensesOverAssets

1.27%

^[1]

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class T Shares

1 Year

rr_ExpenseExampleYear01

180

3 Years

rr_ExpenseExampleYear03

557

5 Years

rr_ExpenseExampleYear05

959

10 Years

rr_ExpenseExampleYear10

2,084

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class T Shares

1 Year

rr_ExpenseExampleNoRedemptionYear01

180

3 Years

rr_ExpenseExampleNoRedemptionYear03

557

5 Years

rr_ExpenseExampleNoRedemptionYear05

959

10 Years

rr_ExpenseExampleNoRedemptionYear10

2,084

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares | Return Before Taxes | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class A Shares

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

^[3]

1 Year

rr_AverageAnnualReturnYear01

(6.24%)

Since Inception

rr_AverageAnnualReturnSinceInception

(5.01%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares | Return Before Taxes | Class C

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class C Shares

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

^[4]

1 Year

rr_AverageAnnualReturnYear01

(2.39%)

Since Inception

rr_AverageAnnualReturnSinceInception

(4.26%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, 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

(0.55%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.62%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, 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

(0.12%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.31%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, 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

(0.44%)

Since Inception

rr_AverageAnnualReturnSinceInception

(4.62%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, 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

(0.43%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.46%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares | Return After Taxes on Distributions | Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class I Shares

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(0.39%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.61%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class I Shares

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

^[5]

1 Year

rr_AverageAnnualReturnYear01

0.46%

Since Inception

rr_AverageAnnualReturnSinceInception

(2.45%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

Janus Emerging Markets Fund | Class A, C, S, I, N, T Shares | MSCI Emerging Markets Index℠ (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

MSCI Emerging Markets Index^SM

1 Year

rr_AverageAnnualReturnYear01

(2.19%)

Since Inception

rr_AverageAnnualReturnSinceInception

(1.54%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2010

[1] Janus Capital has contractually agreed to waive its investment advisory fee and/or reimburse Fund expenses to the extent that 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; brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) exceed 1.11% until at least February 1, 2016. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.

[2] Other Expenses for Class N Shares are based on the estimated annualized expenses that the Shares expect to incur.

[3] Calculated assuming maximum permitted sales loads.

[4] The one year return is calculated to include the contingent deferred sales charge.

[5] 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.