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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 Real Return Fund | Class A, C, S, I, T Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund summary

Janus Real Return Fund
(formerly named Janus Real Return Allocation Fund)
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Janus Real Return Fund seeks real 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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination November 1, 2013
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 45% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 45.00%
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 31 of the Fund’s Prospectus and in the “Purchases” section on page 56 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 or recoupments (if applicable) 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 primarily investing in U.S. Treasury securities, short-duration high-yield/high-risk debt, commodity-linked investments, and equity securities. The Fund’s investments in U.S. Treasury securities may also include Treasury Inflation Protected Securities, also known as TIPS. As utilized by the Fund, each of these types of investments may be considered an “inflation-related investment,” which are those that may provide what is known as “real return,” or a rate of return above the rate of inflation over a full market cycle. Due to the nature of securities in which the Fund invests, it may have relatively high portfolio turnover compared to other funds.

The Fund may invest up to 90% of its net assets in short-duration high-yield/high-risk debt securities. The Fund’s investments in short-duration high-yield/high-risk securities include debt rated below investment grade, also known as “junk bonds.” Securities rated below investment grade may include their unrated equivalents or other high-yielding securities the portfolio managers believe offer attractive risk/return characteristics. The Fund may also invest in certain investment grade debt instruments, including corporate bonds, government bonds, municipal bonds, mortgage-backed securities, zero-coupon bonds, and agency securities. The Fund may invest in foreign debt securities.

To seek exposure to the commodities markets, the Fund may invest in commodity-linked investments such as commodity-related exchange-traded funds (“ETFs”), commodity index-linked swap agreements, commodity options and futures, and options on futures that provide exposure to the investment returns of the commodities markets. The Fund may also invest in other commodity-linked derivative instruments, such as commodity-linked notes (“structured notes”).

The Fund’s investments in equity securities may include common stock, preferred stock, and convertible securities, all of which may include exposure to foreign markets. The Fund may invest in companies of any market capitalization. The Fund’s equity investments may also include securities of real estate-related companies, including, but not limited to, real estate investment trusts (“REITs”) and similar REIT-like entities, such as foreign entities that have REIT characteristics.

The Fund may also invest in derivative instruments (by taking long and/or short positions) for various purposes, including hedging by shorting interest rate futures against long positions in TIPS, using inflation index swaps to hedge against unexpected changes in the rate of inflation, using interest rate swaps to hedge against changes in interest rates, 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, 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 also use reverse repurchase agreements to generate income as part of its inflation-related strategies. Proceeds from reverse repurchase agreement transactions may be invested in other securities or instruments to attempt to increase the Fund’s investment return. The Fund may also invest in money market instruments, buy backs or dollar rolls, other securitized debt products, bank loans, various when-issued securities, exchange-traded notes, and other investment companies.

In addition to considering economic factors such as the rate of inflation and 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 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.

Inflation-Related Investment Risk. Inflation index swaps and other inflation-linked securities are subject to inflation risk. A swap held long by the Fund can potentially lose value if the rate of inflation over the life of the swap is less than the fixed rate that the Fund agrees to pay at the initiation of the swap. Except for the Fund’s investments in U.S. Treasury securities, which are guaranteed as to principal by the U.S. Treasury, the inflation-adjusted principal value of inflation-linked securities repaid at maturity may be less than the original principal. Because of the inflation-linked adjustment feature, inflation-linked securities typically have lower yields than conventional fixed-rate securities. In the event of deflation, where prices decline over time, the principal and income of inflation-linked securities will likely decline, resulting in losses to the Fund.

High-Yield/High-Risk Bond Risk. The Fund may invest up to 90% of its net assets in higher-yielding/higher-risk bonds, also known as “junk” bonds. 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.

Commodity-Linked Investments Risk. The Fund may invest in various commodity-linked investments that provide exposure to the commodities markets. Such exposure may subject the Fund to greater volatility than investments in traditional securities. The value of a given commodity-linked derivative investment typically is based upon the price movements of a physical commodity (such as heating oil, livestock, or agricultural products), a commodity futures contract or commodity index, or some other readily measurable economic variable. The value of commodity-linked derivative instruments may therefore be affected by changes in overall market movements, volatility of the underlying benchmark, changes in interest rates, or other factors affecting a particular industry or commodity such as drought, floods, weather, livestock disease, embargoes, tariffs, and international economic, political, and regulatory developments.

Exchange-Traded Funds Risk. The Fund may invest in ETFs which are typically open-end investment companies that are traded on a national securities exchange. ETFs typically incur fees, such as investment advisory fees 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 securities or commodities 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 or commodities 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.

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.

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.

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.

Leverage Risk. Gains or losses from a derivative can be substantially greater than the derivative’s original cost, and can therefore involve leverage. In particular, certain commodity-linked investments may subject the Fund to leveraged market exposure to commodities. Leverage also occurs when the Fund increases its assets available for investment through borrowings, reverse repurchase agreements, or similar transactions. The Fund’s use of leverage can magnify the effect of any gains or losses, causing the Fund to be more volatile than if it had not been leveraged. There is no assurance that any leveraging strategy will be successful.

Reverse Repurchase Agreement Risk. Reverse repurchase agreements involve leverage risk, counterparty risk, and the risk that the value of securities that the Fund is obligated to repurchase under the agreement may decline below the repurchase price. When the Fund invests reverse repurchase transaction proceeds, the Fund is at risk for any fluctuations in the value of securities in which the proceeds are invested. To the extent the Fund uses reverse repurchase agreements, the value of an investment in the Fund may be more volatile, and such transactions may increase the Fund’s overall investment exposure. Additionally, interest expenses related to reverse repurchase transactions could exceed the rate of return on debt obligations and other investments held by the Fund, thereby reducing returns to shareholders.

Foreign Exposure Risk. The Fund normally has significant 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. 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.

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 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.

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 real estate investment trusts, 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.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio managers 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.

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.

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 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 managers 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.
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 Real Return Fund | Class A, C, S, I, 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 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.70% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.50% [2]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.49% [2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.01% [2]
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class A Shares
1 Year rr_ExpenseExampleYear01 620
3 Years rr_ExpenseExampleYear03 926
5 Years rr_ExpenseExampleYear05 1,253
10 Years rr_ExpenseExampleYear10 2,177
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class A Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 620
3 Years rr_ExpenseExampleNoRedemptionYear03 926
5 Years rr_ExpenseExampleNoRedemptionYear05 1,253
10 Years rr_ExpenseExampleNoRedemptionYear10 2,177
Janus Real Return Fund | Class A, C, S, I, 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 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.69% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.24% [2]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.48% [2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.76% [2]
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class C Shares
1 Year rr_ExpenseExampleYear01 327
3 Years rr_ExpenseExampleYear03 700
5 Years rr_ExpenseExampleYear05 1,199
10 Years rr_ExpenseExampleYear10 2,573
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class C Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 227
3 Years rr_ExpenseExampleNoRedemptionYear03 700
5 Years rr_ExpenseExampleNoRedemptionYear05 1,199
10 Years rr_ExpenseExampleNoRedemptionYear10 2,573
Janus Real Return Fund | Class A, C, S, I, 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 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.94% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.74% [2]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.48% [2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.26% [2]
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class S Shares
1 Year rr_ExpenseExampleYear01 177
3 Years rr_ExpenseExampleYear03 547
5 Years rr_ExpenseExampleYear05 943
10 Years rr_ExpenseExampleYear10 2,049
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class S Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 177
3 Years rr_ExpenseExampleNoRedemptionYear03 547
5 Years rr_ExpenseExampleNoRedemptionYear05 943
10 Years rr_ExpenseExampleNoRedemptionYear10 2,049
Janus Real Return Fund | Class A, C, S, I, 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 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.69% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.24% [2]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.48% [2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 0.76% [2]
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class I Shares
1 Year rr_ExpenseExampleYear01 126
3 Years rr_ExpenseExampleYear03 393
5 Years rr_ExpenseExampleYear05 680
10 Years rr_ExpenseExampleYear10 1,498
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class I Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 126
3 Years rr_ExpenseExampleNoRedemptionYear03 393
5 Years rr_ExpenseExampleNoRedemptionYear05 680
10 Years rr_ExpenseExampleNoRedemptionYear10 1,498
Janus Real Return Fund | Class A, C, S, I, 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 0.55%
Distribution/Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.94% [1]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.49% [2]
Fee Waiver rr_FeeWaiverOrReimbursementOverAssets 0.48% [2]
Total Annual Fund Operating Expenses After Fee Waiver rr_NetExpensesOverAssets 1.01% [2]
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName
Class T Shares
1 Year rr_ExpenseExampleYear01 151
3 Years rr_ExpenseExampleYear03 470
5 Years rr_ExpenseExampleYear05 812
10 Years rr_ExpenseExampleYear10 1,777
Expense Example, No Redemption, By Year, Column [Text] rr_ExpenseExampleNoRedemptionByYearColumnName
Class T Shares
1 Year rr_ExpenseExampleNoRedemptionYear01 151
3 Years rr_ExpenseExampleNoRedemptionYear03 470
5 Years rr_ExpenseExampleNoRedemptionYear05 812
10 Years rr_ExpenseExampleNoRedemptionYear10 1,777
[1] Other Expenses are based on the estimated expenses that the Fund expects to incur.
[2] 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 for Class A Shares, Class C Shares, and Class I Shares); brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 0.76% until at least November 1, 2013. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees. For a period of three years subsequent to the Fund's commencement of operations (May 13, 2011) or until the Fund's assets exceed the first breakpoint in the investment advisory fee schedule, whichever occurs first, Janus Capital may recover from the Fund fees and expenses previously waived or reimbursed, which could then be considered a deferral, if the Fund's expense ratio, including recovered expenses, falls below the expense limit.