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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
(No. 002-34393)	þ
Pre-Effective Amendment No.	o
Post-Effective Amendment No. 184	þ

and/or

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940
(No. 811-01879)	þ
Amendment No. 167	þ

(Check appropriate box or boxes.)

JANUS INVESTMENT FUND

(Exact Name of Registrant as Specified in Charter)

151 Detroit Street, Denver, Colorado
(Address of Principal Executive Offices) 80206-4805
(Zip Code)

Registrant’s Telephone Number, including Area Code: 303-333-3863

Stephanie Grauerholz-Lofton – 151 Detroit Street, Denver, Colorado 80206-4805
(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering:

It is proposed that this filing will become effective (check appropriate box):

þ immediately upon filing pursuant to paragraph (b)

o on (date) pursuant to paragraph (b)

o 60 days after filing pursuant to paragraph (a)(1)

o on (date) pursuant to paragraph (a)(1)

o 75 days after filing pursuant to paragraph (a)(2)

o on (date) pursuant to paragraph (a)(2) of rule 485.

If appropriate, check the following box:

o This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Amendment to its Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Amendment to its Registration Statement to be signed on its behalf by the undersigned, thereto duly authorized, in the City of Denver, and State of Colorado, on the 17^th day of January, 2013.

JANUS INVESTMENT FUND
By:	/s/ Robin C. Beery
	Robin C. Beery, President and
	Chief Executive Officer

     Janus Investment Fund is organized under an Amended and Restated Agreement and Declaration of Trust dated March 18, 2003 (“Declaration of Trust”), a copy of which is on file with the Secretary of State of The Commonwealth of Massachusetts. The obligations of the Registrant hereunder are not binding upon any of the Trustees, shareholders, nominees, officers, agents or employees of the Registrant personally, but bind only the trust property of the Registrant, as provided in the Declaration of Trust of the Registrant. The execution of this Amendment to the Registration Statement has been authorized by the Trustees of the Registrant and this Amendment to the Registration Statement has been signed by an authorized officer of the Registrant, acting as such, and neither such authorization by such Trustees nor such execution by such officer shall be deemed to have been made by any of them personally, but shall bind only the trust property of the Registrant as provided in its Declaration of Trust.

     Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/ Robin C. Beery Robin C. Beery	President and Chief Executive Officer (Principal Executive Officer)	January 17, 2013
/s/ Jesper Nergaard Jesper Nergaard	Vice President, Chief Financial Officer, Treasurer and Principal Accounting Officer (Principal Financial Officer and Principal Accounting Officer)	January 17, 2013

C-1

Signature	Title	Date
William F. McCalpin* William F. McCalpin	Chairman and Trustee	January 17, 2013
William D. Cvengros* William D. Cvengros	Trustee	January 17, 2013
James T. Rothe* James T. Rothe	Trustee	January 17, 2013
William D. Stewart* William D. Stewart	Trustee	January 17, 2013
Linda S. Wolf* Linda S. Wolf	Trustee	January 17, 2013

/s/ Stephanie Grauerholz-Lofton
*By:	Stephanie Grauerholz-Lofton
	Attorney-in-Fact

Pursuant to Powers of Attorney, dated April 11, 2008, incorporated by reference to Exhibit 15(c) to Post-Effective Amendment No. 123, filed on February 27, 2009; Power of Attorney, dated June 24, 2010, incorporated by reference to Exhibit (q)(4) to Post-Effective Amendment No. 132, filed on July 30, 2010; and Power of Attorney, dated January 5, 2011, incorporated by reference to Exhibit (q)(5) to Post-Effective Amendment No. 138, filed on January 28, 2011

C-2

INDEX OF EXHIBITS

Exhibit Number	Exhibit Title
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase

C-3

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Janus Diversified Alternatives Fund | Class D Shares

FUND SUMMARY

Janus Diversified Alternatives Fund

INVESTMENT OBJECTIVE

Janus Diversified Alternatives Fund seeks absolute return with low correlation to stocks and bonds.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		Janus Diversified Alternatives Fund Class D Shares Class D
Operating Expenses Column [Text]		Class D
Management Fees of the Fund and the Subsidiary	[1]	1.00%
Other Expenses	[2]	0.57%
Other Expenses of the Fund		0.55%
Other Expenses of the Subsidiary		0.02%
Total Annual Fund Operating Expenses	[3]	1.57%
Fee Waiver	[3]	0.19%
Total Annual Fund Operating Expenses After Fee Waiver	[3]	1.38%

EXAMPLE:

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.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers 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 (USD $)	Expense Example, By Year, Column [Text]	1 Year	3 Years
Janus Diversified Alternatives Fund Class D Shares Class D	Class D Shares	160	496

Portfolio Turnover:

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.

PRINCIPAL INVESTMENT STRATEGIES

Under normal market conditions, the Fund pursues its investment objective by investing in a diverse group of return drivers, each a type of risk premium (collectively, “risk premia”), across equity, fixed income, commodity, and currency asset classes. Risk premia refers to the return that is expected for assuming a particular market risk. For example, investors expect a higher return in exchange for the perceived risks associated with investing in emerging markets as compared to investing in developed markets. Accordingly, a belief that emerging market equities may outperform developed market equities presents a risk premia opportunity. The Fund seeks to generate returns by identifying and isolating diverse sources of potential risk premia, and combining these individual risk premia into a liquid portfolio that delivers consistent, absolute returns with a low correlation to the returns generated by investments in stocks and bonds.

The Fund employs a proprietary multi-factor process to allocate the Fund’s assets across the various risk premia. The process begins with an approximate equal-weighted risk to each risk premia in which the Fund invests, so that no individual risk premia contributes disproportionately to the Fund’s risk profile and expected returns over the long term. Next, the Fund applies additional advanced allocation methodologies to the portfolio to tactically adjust the weights of individual risk premia. The risk premia allocations are rebalanced from time to time, and depending on market conditions and the portfolio managers’ beliefs regarding the expected returns, relative risk and correlation properties of one or more individual risk premia, the Fund may not utilize all identified risk premia in its investment process at all times. Janus Capital believes that this allocation process may provide better risk adjusted returns than a traditional asset allocation strategy that employs fixed weights for asset classes.

The Fund employs various strategies within the equity, fixed income, commodity, and currency asset classes to identify risk premia and generate returns, including, but not limited to, relative value, momentum, credit, size, roll yield, systematic, and currency carry.

Relative Value – Relative Value investing seeks to capture the spread between a relatively undervalued asset and a more expensive one. For example, one pool of equities often outperforms another pool of equities in a different sector or investment style. Relative value attempts to identify the difference in valuation associated with those assets and favors investments in the relatively undervalued pool to generate return.

Momentum – Momentum investing seeks to capitalize on the expected continuance of trends in the market. For example, if interest rates are increasing, a momentum investor would invest in securities that would generate positive returns if rates continue to increase in the near term.

Credit – Credit investing seeks to invest in fixed-income securities to realize the additional rate of return that corporate debt provides as compared to U.S. Treasuries.

Size – Size investing seeks to generate returns by investing in small capitalization equity securities over large capitalization equity securities. The basis for this strategy is that over time, less liquid equities (small capitalization) will outperform more liquid equities (large capitalization).

Roll Yield – Roll Yield investing seeks to capture returns from favoring certain maturities of commodity futures contracts over others. This strategy typically combines offsetting long and short exposures on various sets of individual commodity futures contracts that have different expiration dates.

Systematic – Systematic investing seeks to invest in one or more asset classes, or a subset of a specific asset class, to generate the associated market return. For example, the Fund may invest a portion of the portfolio in global equities to generate the market returns associated with that type of investment.

Currency Carry – Currency Carry investing seeks to generate returns by investing in higher yielding currencies versus lower yielding currencies. In a carry trade, low interest rate currencies may be sold, and high interest rate currencies may be purchased.

As part of the process to identify and isolate specific risk premia and generate returns, the Fund may have both long and short exposure to securities in which it invests with respect to a risk premia. The Fund’s exposure to U.S. and non-U.S. investments, which may include emerging markets, will vary based on perceived investment opportunities and the portfolio managers’ global investment outlook. The Fund will make significant use of derivative instruments, 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. Derivatives will be used to gain exposure to the various asset classes in which the Fund may invest, to generate returns, for hedging purposes (to offset risks associated with an investment, currency exposure, or market conditions), to adjust currency exposure relative to a benchmark index, and to earn income and enhance returns. The Fund may utilize swaps, including equity, interest rate, currency, and total return swaps. The Fund may utilize options and futures, including forward commodity and currency contracts and U.S. Treasury, interest rate, and market index futures. The Fund’s use of options includes options purchased and sold (written). The Fund’s exposure to derivatives will vary and is not limited to those derivatives listed. 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, when available.

The Fund’s exposure to derivatives will create a leveraging effect on the portfolio where market exposure exceeds amounts invested. This leverage will vary over time and may at times be significant. The Fund may have a substantial cash position due to margin and collateral requirements related to the Fund’s use of derivatives. Such margin and collateral requirements may limit the Fund’s ability to take advantage of other investment opportunities and may negatively affect the Fund’s ability to achieve its investment objective.

The Fund’s equity and fixed-income exposure may be obtained through direct investment in equity and fixed-income securities or through investment in other Janus mutual funds, unaffiliated mutual funds, or exchange-traded funds (“ETFs”). The Fund may also utilize exchange-traded notes (“ETNs”). The equity securities or underlying equity funds in which the Fund invests may involve exposure to common stocks of companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The fixed-income securities or underlying fixed-income funds in which the Fund invests may include securities of any maturity and of any credit quality, and may include exposure to government bonds, corporate bonds, convertible bonds, mortgage-backed securities, zero-coupon bonds, and high-yield/high-risk bonds, also known as “junk” bonds. The Fund’s investment in ETFs and ETNs may be used to gain exposure to market indices, a basket of securities, commodities, currencies, or a particular commodity or currency.

The Fund’s exposure to the commodity markets, in whole or in part, may be made through investment in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”), which is generally subject to the same investment policies and restrictions as the Fund. The Subsidiary will invest in commodity-related derivatives such as futures and swaps, ETNs, and other investments such as cash or U.S. Treasuries which may serve as margin or collateral for the Subsidiary’s commodity-linked derivative positions.

Due to the nature of the investment process and the types of securities in which the Fund may invest, it may have high portfolio turnover compared to other funds.

PRINCIPAL INVESTMENT RISKS

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a portfolio which includes exposure to equity (such as stocks or any other security representing an ownership interest), fixed-income (such as bonds, notes, and debentures), commodities, and currency asset classes, and which involves the use of derivatives. Such investments, and derivatives in particular, tend to be more volatile than many other investment choices.

Management Risk. The Fund’s ability to achieve its investment objective depends largely upon the portfolio managers’ successful evaluation of the risks, potential returns, and correlation properties with respect to the various risk premia in which the Fund invests. There is a risk that the returns provided by individual risk premia may be subject to high volatility and that the portfolio managers’ beliefs about the risk, expected returns and correlation properties of one or more individual risk premia may be incorrect. Further, the Fund’s ability to achieve its investment objective also depends on the successful allocation of the Fund’s assets among various risk premia and asset classes, and you could lose money on your investment in the Fund as a result of these allocations. There is also a risk that the Fund’s investments will correlate with the performance of stocks and bonds to a greater degree than anticipated, and the Fund will not meet its investment objective. Finally, Janus Capital does not have prior experience managing a risk premia investment strategy, and there is no guarantee that the investment techniques and analysis used by the Fund’s portfolio managers will produce the desired results.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual investment, or multiple investments, in the portfolio decreases at the same time. Further, while the Fund’s goal is to produce returns that have a low correlation to the stock and bond markets, you should understand that regardless of how well the Fund’s individual investments perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The value of your investment in the Fund may fall, sometimes sharply, in response to changes in the market, and you could lose money. Because the Fund seeks to produce returns that have a low correlation to the returns generated by the stock and bond markets, the Fund may underperform these markets when these markets rise sharply or experience prolonged periods of outperformance. Additionally, the Fund’s performance may be negatively affected during prolonged periods when the returns provided by the risk premia are consistently low.

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.

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, short sales, 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.

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

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.

Commodity-Linked Investments Risk. The Fund may invest, directly or indirectly, 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.

Subsidiary Risk. By investing in the Subsidiary, the Fund will be indirectly exposed to the risks associated with the Subsidiary’s investments, which are generally similar to those that are permitted to be held by the Fund. The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the “1940 Act”), and is not subject to all of the provisions of the 1940 Act. The Internal Revenue Service (“IRS”) has previously issued a number of private letter rulings to mutual funds (but not the Fund), which indicate that income from a fund’s investment in a wholly-owned foreign subsidiary that invests in commodity-linked derivatives, such as the Subsidiary, constitutes qualifying income. Changes in the laws of the United States and/or the Cayman Islands could result in the inability of the Fund and/or the Subsidiary to operate as described in the Fund’s Prospectus and the Statement of Additional Information. Such changes could adversely affect the Fund’s ability to meet its investment objective and jeopardize the Fund’s status as a regulated investment company under the U.S. tax code, which in turn may subject the Fund to higher tax rates and/or penalties.

Foreign Exposure Risk. The Fund normally has 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 or an underlying mutual fund or ETF 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 exposure to emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

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

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.

Fixed-Income Securities Risk. The Fund may invest in a variety of fixed-income securities, either directly or indirectly through underlying mutual funds and ETFs. 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.

Currency Risk. The Fund’s investments and strategies will involve exposure to foreign currencies. Currency risk is the risk that changes in the exchange rate between currencies will adversely affect the value (in U.S. dollar terms) of an investment. As long as the Fund holds a foreign security, its value will be affected by the value of the local currency relative to the U.S. dollar. When the Fund sells a foreign currency denominated security, its value may be worth less in U.S. dollars even if the security increases in value in its home country. U.S. dollar-denominated securities of foreign issuers may also be affected by currency risk, as the value of these securities may also be affected by changes in the issuer’s local currency. Additionally, and as a result of the Fund’s use of currency investment strategies, the Fund’s net currency positions may expose the Fund to losses independent of any securities positions.

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.

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.

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, fixed-income risk, and commodity-linked investments risk.

Exchange-Traded Notes Risk. The Fund may invest in ETNs, which are debt securities whose returns are linked to a particular index. ETNs are typically linked to the performance of a commodities index that reflects the potential return on unleveraged investments in futures contracts of physical commodities, plus a specified rate of interest that could be earned on cash collateral. ETNs are subject to credit risk and counterparty risk. The value of an ETN may vary and may be influenced by time to maturity, level of supply and demand for the ETN, volatility and lack of liquidity in underlying commodities markets, changes in the applicable interest rates, changes in the issuer’s credit rating, and economic, legal, political, or geographic events that affect the referenced commodity. When the Fund invests in ETNs it will bear its proportionate share of any fees and expenses borne by the ETN. There may be restrictions on the Fund’s right to redeem its investment in an ETN, which is meant to be held until maturity. The Fund’s decision to sell its ETN holdings may be limited by the availability of a secondary market.

Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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.

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

PERFORMANCE INFORMATION

The Fund does not have a full calendar year of operations. Performance information for certain periods will be included in the Fund’s first annual and/or semiannual report.

[1] The Fund may invest in commodity-linked investments through a wholly-owned subsidiary of the Fund that invests in commodity-linked investments. Janus Capital has contractually agreed that to the extent the Fund invests in the subsidiary, it shall not collect advisory fees from the Fund in an amount equal to the fee it collects from the subsidiary. The management fee waiver arrangement may not be discontinued by Janus Capital as long as its contract with the subsidiary is in place.

[2] Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.

[3] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses, which include the other expenses of the subsidiary shown above (excluding administrative services fees payable pursuant to the Transfer Agency Agreement, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) to 1.25% until at least November 1, 2014. 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 (December 28, 2012) 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.

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Janus Diversified Alternatives Fund | Class A, C, S, I, N, T Shares

FUND SUMMARY

Janus Diversified Alternatives Fund

INVESTMENT OBJECTIVE

Janus Diversified Alternatives Fund seeks absolute return with low correlation to stocks and bonds.

FEES AND EXPENSES OF THE FUND

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.

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 32 of the Fund’s Prospectus and in the “Purchases” section on page 56 of the Fund’s Statement of Additional Information.

SHAREHOLDER FEES
(fees paid directly from your investment)

Shareholder Fees Janus Diversified Alternatives Fund Class A, C, S, I, N, T Shares	Class A	Class C	Class S	Class I	Class N	Class T
Shareholder Fees Column [Text]	Class A	Class C	Class S	Class I	Class N	Class T
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	5.75%	none	none	none	none	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	none	1.00%	none	none	none	none

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Janus Diversified Alternatives Fund Class A, C, S, I, N, T Shares		Class A	Class C	Class S	Class I	Class N	Class T
Operating Expenses Column [Text]		Class A	Class C	Class S	Class I	Class N	Class T
Management Fees of the Fund and the Subsidiary	[1]	1.00%	1.00%	1.00%	1.00%	1.00%	1.00%
Distribution/Service (12b-1) Fees		0.25%	1.00%	0.25%	none	none	none
Other Expenses	[2]	0.44%	0.56%	0.55%	0.37%	0.30%	0.55%
Other Expenses of the Fund		0.42%	0.54%	0.53%	0.35%	0.28%	0.53%
Other Expenses of the Subsidiary		0.02%	0.02%	0.02%	0.02%	0.02%	0.02%
Total Annual Fund Operating Expenses	[3]	1.69%	2.56%	1.80%	1.37%	1.30%	1.55%
Fee Waiver	[3]	0.09%	0.14%	0.05%	0.07%	0.05%	0.05%
Total Annual Fund Operating Expenses After Fee Waiver	[3]	1.60%	2.42%	1.75%	1.30%	1.25%	1.50%

EXAMPLE:

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.

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:

If Shares are redeemed:

Expense Example Janus Diversified Alternatives Fund Class A, C, S, I, N, T Shares (USD $)	Expense Example, By Year, Column [Text]	1 Year	3 Years
Class A	Class A Shares	737	1,077
Class C	Class C Shares	359	796
Class S	Class S Shares	183	566
Class I	Class I Shares	139	434
Class N	Class N Shares	132	412
Class T	Class T Shares	158	490

If Shares are not redeemed:

Expense Example, No Redemption Janus Diversified Alternatives Fund Class A, C, S, I, N, T Shares (USD $)	Expense Example, No Redemption, By Year, Column [Text]	1 Year	3 Years
Class A	Class A Shares	737	1,077
Class C	Class C Shares	259	796
Class S	Class S Shares	183	566
Class I	Class I Shares	139	434
Class N	Class N Shares	132	412
Class T	Class T Shares	158	490

Portfolio Turnover:

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.

PRINCIPAL INVESTMENT STRATEGIES

Under normal market conditions, the Fund pursues its investment objective by investing in a diverse group of return drivers, each a type of risk premium (collectively, “risk premia”), across equity, fixed income, commodity, and currency asset classes. Risk premia refers to the return that is expected for assuming a particular market risk. For example, investors expect a higher return in exchange for the perceived risks associated with investing in emerging markets as compared to investing in developed markets. Accordingly, a belief that emerging market equities may outperform developed market equities presents a risk premia opportunity. The Fund seeks to generate returns by identifying and isolating diverse sources of potential risk premia, and combining these individual risk premia into a liquid portfolio that delivers consistent, absolute returns with a low correlation to the returns generated by investments in stocks and bonds.

The Fund employs a proprietary multi-factor process to allocate the Fund’s assets across the various risk premia. The process begins with an approximate equal-weighted risk to each risk premia in which the Fund invests, so that no individual risk premia contributes disproportionately to the Fund’s risk profile and expected returns over the long term. Next, the Fund applies additional advanced allocation methodologies to the portfolio to tactically adjust the weights of individual risk premia. The risk premia allocations are rebalanced from time to time, and depending on market conditions and the portfolio managers’ beliefs regarding the expected returns, relative risk and correlation properties of one or more individual risk premia, the Fund may not utilize all identified risk premia in its investment process at all times. Janus Capital believes that this allocation process may provide better risk adjusted returns than a traditional asset allocation strategy that employs fixed weights for asset classes.

The Fund employs various strategies within the equity, fixed income, commodity, and currency asset classes to identify risk premia and generate returns, including, but not limited to, relative value, momentum, credit, size, roll yield, systematic, and currency carry.

Relative Value – Relative Value investing seeks to capture the spread between a relatively undervalued asset and a more expensive one. For example, one pool of equities often outperforms another pool of equities in a different sector or investment style. Relative value attempts to identify the difference in valuation associated with those assets and favors investments in the relatively undervalued pool to generate return.

Momentum – Momentum investing seeks to capitalize on the expected continuance of trends in the market. For example, if interest rates are increasing, a momentum investor would invest in securities that would generate positive returns if rates continue to increase in the near term.

Credit – Credit investing seeks to invest in fixed-income securities to realize the additional rate of return that corporate debt provides as compared to U.S. Treasuries.

Size – Size investing seeks to generate returns by investing in small capitalization equity securities over large capitalization equity securities. The basis for this strategy is that over time, less liquid equities (small capitalization) will outperform more liquid equities (large capitalization).

Roll Yield – Roll Yield investing seeks to capture returns from favoring certain maturities of commodity futures contracts over others. This strategy typically combines offsetting long and short exposures on various sets of individual commodity futures contracts that have different expiration dates.

Systematic – Systematic investing seeks to invest in one or more asset classes, or a subset of a specific asset class, to generate the associated market return. For example, the Fund may invest a portion of the portfolio in global equities to generate the market returns associated with that type of investment.

Currency Carry – Currency Carry investing seeks to generate returns by investing in higher yielding currencies versus lower yielding currencies. In a carry trade, low interest rate currencies may be sold, and high interest rate currencies may be purchased.

As part of the process to identify and isolate specific risk premia and generate returns, the Fund may have both long and short exposure to securities in which it invests with respect to a risk premia. The Fund’s exposure to U.S. and non-U.S. investments, which may include emerging markets, will vary based on perceived investment opportunities and the portfolio managers’ global investment outlook. The Fund will make significant use of derivative instruments, 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. Derivatives will be used to gain exposure to the various asset classes in which the Fund may invest, to generate returns, for hedging purposes (to offset risks associated with an investment, currency exposure, or market conditions), to adjust currency exposure relative to a benchmark index, and to earn income and enhance returns. The Fund may utilize swaps, including equity, interest rate, currency, and total return swaps. The Fund may utilize options and futures, including forward commodity and currency contracts and U.S. Treasury, interest rate, and market index futures. The Fund’s use of options includes options purchased and sold (written). The Fund’s exposure to derivatives will vary and is not limited to those derivatives listed. 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, when available.

The Fund’s exposure to derivatives will create a leveraging effect on the portfolio where market exposure exceeds amounts invested. This leverage will vary over time and may at times be significant. The Fund may have a substantial cash position due to margin and collateral requirements related to the Fund’s use of derivatives. Such margin and collateral requirements may limit the Fund’s ability to take advantage of other investment opportunities and may negatively affect the Fund’s ability to achieve its investment objective.

The Fund’s equity and fixed-income exposure may be obtained through direct investment in equity and fixed-income securities or through investment in other Janus mutual funds, unaffiliated mutual funds, or exchange-traded funds (“ETFs”). The Fund may also utilize exchange-traded notes (“ETNs”). The equity securities or underlying equity funds in which the Fund invests may involve exposure to common stocks of companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The fixed-income securities or underlying fixed-income funds in which the Fund invests may include securities of any maturity and of any credit quality, and may include exposure to government bonds, corporate bonds, convertible bonds, mortgage-backed securities, zero-coupon bonds, and high-yield/high-risk bonds, also known as “junk” bonds. The Fund’s investment in ETFs and ETNs may be used to gain exposure to market indices, a basket of securities, commodities, currencies, or a particular commodity or currency.

The Fund’s exposure to the commodity markets, in whole or in part, may be made through investment in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”), which is generally subject to the same investment policies and restrictions as the Fund. The Subsidiary will invest in commodity-related derivatives such as futures and swaps, ETNs, and other investments such as cash or U.S. Treasuries which may serve as margin or collateral for the Subsidiary’s commodity-linked derivative positions.

Due to the nature of the investment process and the types of securities in which the Fund may invest, it may have high portfolio turnover compared to other funds.

PRINCIPAL INVESTMENT RISKS

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a portfolio which includes exposure to equity (such as stocks or any other security representing an ownership interest), fixed-income (such as bonds, notes, and debentures), commodities, and currency asset classes, and which involves the use of derivatives. Such investments, and derivatives in particular, tend to be more volatile than many other investment choices.

Management Risk. The Fund’s ability to achieve its investment objective depends largely upon the portfolio managers’ successful evaluation of the risks, potential returns, and correlation properties with respect to the various risk premia in which the Fund invests. There is a risk that the returns provided by individual risk premia may be subject to high volatility and that the portfolio managers’ beliefs about the risk, expected returns and correlation properties of one or more individual risk premia may be incorrect. Further, the Fund’s ability to achieve its investment objective also depends on the successful allocation of the Fund’s assets among various risk premia and asset classes, and you could lose money on your investment in the Fund as a result of these allocations. There is also a risk that the Fund’s investments will correlate with the performance of stocks and bonds to a greater degree than anticipated, and the Fund will not meet its investment objective. Finally, Janus Capital does not have prior experience managing a risk premia investment strategy, and there is no guarantee that the investment techniques and analysis used by the Fund’s portfolio managers will produce the desired results.

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual investment, or multiple investments, in the portfolio decreases at the same time. Further, while the Fund’s goal is to produce returns that have a low correlation to the stock and bond markets, you should understand that regardless of how well the Fund’s individual investments perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The value of your investment in the Fund may fall, sometimes sharply, in response to changes in the market, and you could lose money. Because the Fund seeks to produce returns that have a low correlation to the returns generated by the stock and bond markets, the Fund may underperform these markets when these markets rise sharply or experience prolonged periods of outperformance. Additionally, the Fund’s performance may be negatively affected during prolonged periods when the returns provided by the risk premia are consistently low.

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.

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, short sales, 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.

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

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.

Commodity-Linked Investments Risk. The Fund may invest, directly or indirectly, 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.

Subsidiary Risk. By investing in the Subsidiary, the Fund will be indirectly exposed to the risks associated with the Subsidiary’s investments, which are generally similar to those that are permitted to be held by the Fund. The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the “1940 Act”), and is not subject to all of the provisions of the 1940 Act. The Internal Revenue Service (“IRS”) has previously issued a number of private letter rulings to mutual funds (but not the Fund), which indicate that income from a fund’s investment in a wholly-owned foreign subsidiary that invests in commodity-linked derivatives, such as the Subsidiary, constitutes qualifying income. Changes in the laws of the United States and/or the Cayman Islands could result in the inability of the Fund and/or the Subsidiary to operate as described in the Fund’s Prospectus and the Statement of Additional Information. Such changes could adversely affect the Fund’s ability to meet its investment objective and jeopardize the Fund’s status as a regulated investment company under the U.S. tax code, which in turn may subject the Fund to higher tax rates and/or penalties.

Foreign Exposure Risk. The Fund normally has 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 or an underlying mutual fund or ETF 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 exposure to emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

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

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.

Fixed-Income Securities Risk. The Fund may invest in a variety of fixed-income securities, either directly or indirectly through underlying mutual funds and ETFs. 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.

Currency Risk. The Fund’s investments and strategies will involve exposure to foreign currencies. Currency risk is the risk that changes in the exchange rate between currencies will adversely affect the value (in U.S. dollar terms) of an investment. As long as the Fund holds a foreign security, its value will be affected by the value of the local currency relative to the U.S. dollar. When the Fund sells a foreign currency denominated security, its value may be worth less in U.S. dollars even if the security increases in value in its home country. U.S. dollar-denominated securities of foreign issuers may also be affected by currency risk, as the value of these securities may also be affected by changes in the issuer’s local currency. Additionally, and as a result of the Fund’s use of currency investment strategies, the Fund’s net currency positions may expose the Fund to losses independent of any securities positions.

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.

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.

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, fixed-income risk, and commodity-linked investments risk.

Exchange-Traded Notes Risk. The Fund may invest in ETNs, which are debt securities whose returns are linked to a particular index. ETNs are typically linked to the performance of a commodities index that reflects the potential return on unleveraged investments in futures contracts of physical commodities, plus a specified rate of interest that could be earned on cash collateral. ETNs are subject to credit risk and counterparty risk. The value of an ETN may vary and may be influenced by time to maturity, level of supply and demand for the ETN, volatility and lack of liquidity in underlying commodities markets, changes in the applicable interest rates, changes in the issuer’s credit rating, and economic, legal, political, or geographic events that affect the referenced commodity. When the Fund invests in ETNs it will bear its proportionate share of any fees and expenses borne by the ETN. There may be restrictions on the Fund’s right to redeem its investment in an ETN, which is meant to be held until maturity. The Fund’s decision to sell its ETN holdings may be limited by the availability of a secondary market.

Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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.

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

PERFORMANCE INFORMATION

The Fund does not have a full calendar year of operations. Performance information for certain periods will be included in the Fund’s first annual and/or semiannual report.

[1] The Fund may invest in commodity-linked investments through a wholly-owned subsidiary of the Fund that invests in commodity-linked investments. Janus Capital has contractually agreed that to the extent the Fund invests in the subsidiary, it shall not collect advisory fees from the Fund in an amount equal to the fee it collects from the subsidiary. The management fee waiver arrangement may not be discontinued by Janus Capital as long as its contract with the subsidiary is in place.

[2] Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.

[3] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses, which include the other expenses of the subsidiary shown above (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; brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 1.25% until at least November 1, 2014. 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 (December 28, 2012) 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.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Prospectus Date	rr_ProspectusDate	Dec. 28, 2012
Janus Diversified Alternatives Fund | Class A, C, S, I, N, T Shares
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	FUND SUMMARY Janus Diversified Alternatives Fund
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Janus Diversified Alternatives Fund seeks absolute return with low correlation to stocks and bonds.
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, 2014
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.
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 32 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
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.
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	Under normal market conditions, the Fund pursues its investment objective by investing in a diverse group of return drivers, each a type of risk premium (collectively, “risk premia”), across equity, fixed income, commodity, and currency asset classes. Risk premia refers to the return that is expected for assuming a particular market risk. For example, investors expect a higher return in exchange for the perceived risks associated with investing in emerging markets as compared to investing in developed markets. Accordingly, a belief that emerging market equities may outperform developed market equities presents a risk premia opportunity. The Fund seeks to generate returns by identifying and isolating diverse sources of potential risk premia, and combining these individual risk premia into a liquid portfolio that delivers consistent, absolute returns with a low correlation to the returns generated by investments in stocks and bonds. The Fund employs a proprietary multi-factor process to allocate the Fund’s assets across the various risk premia. The process begins with an approximate equal-weighted risk to each risk premia in which the Fund invests, so that no individual risk premia contributes disproportionately to the Fund’s risk profile and expected returns over the long term. Next, the Fund applies additional advanced allocation methodologies to the portfolio to tactically adjust the weights of individual risk premia. The risk premia allocations are rebalanced from time to time, and depending on market conditions and the portfolio managers’ beliefs regarding the expected returns, relative risk and correlation properties of one or more individual risk premia, the Fund may not utilize all identified risk premia in its investment process at all times. Janus Capital believes that this allocation process may provide better risk adjusted returns than a traditional asset allocation strategy that employs fixed weights for asset classes. The Fund employs various strategies within the equity, fixed income, commodity, and currency asset classes to identify risk premia and generate returns, including, but not limited to, relative value, momentum, credit, size, roll yield, systematic, and currency carry. Relative Value – Relative Value investing seeks to capture the spread between a relatively undervalued asset and a more expensive one. For example, one pool of equities often outperforms another pool of equities in a different sector or investment style. Relative value attempts to identify the difference in valuation associated with those assets and favors investments in the relatively undervalued pool to generate return. Momentum – Momentum investing seeks to capitalize on the expected continuance of trends in the market. For example, if interest rates are increasing, a momentum investor would invest in securities that would generate positive returns if rates continue to increase in the near term. Credit – Credit investing seeks to invest in fixed-income securities to realize the additional rate of return that corporate debt provides as compared to U.S. Treasuries. Size – Size investing seeks to generate returns by investing in small capitalization equity securities over large capitalization equity securities. The basis for this strategy is that over time, less liquid equities (small capitalization) will outperform more liquid equities (large capitalization). Roll Yield – Roll Yield investing seeks to capture returns from favoring certain maturities of commodity futures contracts over others. This strategy typically combines offsetting long and short exposures on various sets of individual commodity futures contracts that have different expiration dates. Systematic – Systematic investing seeks to invest in one or more asset classes, or a subset of a specific asset class, to generate the associated market return. For example, the Fund may invest a portion of the portfolio in global equities to generate the market returns associated with that type of investment. Currency Carry – Currency Carry investing seeks to generate returns by investing in higher yielding currencies versus lower yielding currencies. In a carry trade, low interest rate currencies may be sold, and high interest rate currencies may be purchased. As part of the process to identify and isolate specific risk premia and generate returns, the Fund may have both long and short exposure to securities in which it invests with respect to a risk premia. The Fund’s exposure to U.S. and non-U.S. investments, which may include emerging markets, will vary based on perceived investment opportunities and the portfolio managers’ global investment outlook. The Fund will make significant use of derivative instruments, 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. Derivatives will be used to gain exposure to the various asset classes in which the Fund may invest, to generate returns, for hedging purposes (to offset risks associated with an investment, currency exposure, or market conditions), to adjust currency exposure relative to a benchmark index, and to earn income and enhance returns. The Fund may utilize swaps, including equity, interest rate, currency, and total return swaps. The Fund may utilize options and futures, including forward commodity and currency contracts and U.S. Treasury, interest rate, and market index futures. The Fund’s use of options includes options purchased and sold (written). The Fund’s exposure to derivatives will vary and is not limited to those derivatives listed. 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, when available. The Fund’s exposure to derivatives will create a leveraging effect on the portfolio where market exposure exceeds amounts invested. This leverage will vary over time and may at times be significant. The Fund may have a substantial cash position due to margin and collateral requirements related to the Fund’s use of derivatives. Such margin and collateral requirements may limit the Fund’s ability to take advantage of other investment opportunities and may negatively affect the Fund’s ability to achieve its investment objective. The Fund’s equity and fixed-income exposure may be obtained through direct investment in equity and fixed-income securities or through investment in other Janus mutual funds, unaffiliated mutual funds, or exchange-traded funds (“ETFs”). The Fund may also utilize exchange-traded notes (“ETNs”). The equity securities or underlying equity funds in which the Fund invests may involve exposure to common stocks of companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The fixed-income securities or underlying fixed-income funds in which the Fund invests may include securities of any maturity and of any credit quality, and may include exposure to government bonds, corporate bonds, convertible bonds, mortgage-backed securities, zero-coupon bonds, and high-yield/high-risk bonds, also known as “junk” bonds. The Fund’s investment in ETFs and ETNs may be used to gain exposure to market indices, a basket of securities, commodities, currencies, or a particular commodity or currency. The Fund’s exposure to the commodity markets, in whole or in part, may be made through investment in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”), which is generally subject to the same investment policies and restrictions as the Fund. The Subsidiary will invest in commodity-related derivatives such as futures and swaps, ETNs, and other investments such as cash or U.S. Treasuries which may serve as margin or collateral for the Subsidiary’s commodity-linked derivative positions. Due to the nature of the investment process and the types of securities in which the Fund may invest, it may have high portfolio turnover compared to other funds.
Risk [Heading]	rr_RiskHeading	PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a portfolio which includes exposure to equity (such as stocks or any other security representing an ownership interest), fixed-income (such as bonds, notes, and debentures), commodities, and currency asset classes, and which involves the use of derivatives. Such investments, and derivatives in particular, tend to be more volatile than many other investment choices. Management Risk. The Fund’s ability to achieve its investment objective depends largely upon the portfolio managers’ successful evaluation of the risks, potential returns, and correlation properties with respect to the various risk premia in which the Fund invests. There is a risk that the returns provided by individual risk premia may be subject to high volatility and that the portfolio managers’ beliefs about the risk, expected returns and correlation properties of one or more individual risk premia may be incorrect. Further, the Fund’s ability to achieve its investment objective also depends on the successful allocation of the Fund’s assets among various risk premia and asset classes, and you could lose money on your investment in the Fund as a result of these allocations. There is also a risk that the Fund’s investments will correlate with the performance of stocks and bonds to a greater degree than anticipated, and the Fund will not meet its investment objective. Finally, Janus Capital does not have prior experience managing a risk premia investment strategy, and there is no guarantee that the investment techniques and analysis used by the Fund’s portfolio managers will produce the desired results. Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual investment, or multiple investments, in the portfolio decreases at the same time. Further, while the Fund’s goal is to produce returns that have a low correlation to the stock and bond markets, you should understand that regardless of how well the Fund’s individual investments perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The value of your investment in the Fund may fall, sometimes sharply, in response to changes in the market, and you could lose money. Because the Fund seeks to produce returns that have a low correlation to the returns generated by the stock and bond markets, the Fund may underperform these markets when these markets rise sharply or experience prolonged periods of outperformance. Additionally, the Fund’s performance may be negatively affected during prolonged periods when the returns provided by the risk premia are consistently low. 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. 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, short sales, 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. Short Sales Risk. Short sales are speculative transactions and involve special risks, including a greater reliance on the portfolio managers’ ability to accurately anticipate the future value of a security. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. The Fund’s losses are potentially unlimited in a short sale transaction. The use of short sales may also cause the Fund to have higher expenses than those of other funds. In addition, due to the investment process of long and short positions, the Fund may be subject to additional transaction costs that may lower the Fund’s returns. The Fund’s use of short sales may also have a leveraging effect on the Fund’s portfolio. 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. Commodity-Linked Investments Risk. The Fund may invest, directly or indirectly, 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. Subsidiary Risk. By investing in the Subsidiary, the Fund will be indirectly exposed to the risks associated with the Subsidiary’s investments, which are generally similar to those that are permitted to be held by the Fund. The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the “1940 Act”), and is not subject to all of the provisions of the 1940 Act. The Internal Revenue Service (“IRS”) has previously issued a number of private letter rulings to mutual funds (but not the Fund), which indicate that income from a fund’s investment in a wholly-owned foreign subsidiary that invests in commodity-linked derivatives, such as the Subsidiary, constitutes qualifying income. Changes in the laws of the United States and/or the Cayman Islands could result in the inability of the Fund and/or the Subsidiary to operate as described in the Fund’s Prospectus and the Statement of Additional Information. Such changes could adversely affect the Fund’s ability to meet its investment objective and jeopardize the Fund’s status as a regulated investment company under the U.S. tax code, which in turn may subject the Fund to higher tax rates and/or penalties. Foreign Exposure Risk. The Fund normally has 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 or an underlying mutual fund or ETF 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 exposure to emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries. Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve other risks. 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. Fixed-Income Securities Risk. The Fund may invest in a variety of fixed-income securities, either directly or indirectly through underlying mutual funds and ETFs. 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. Currency Risk. The Fund’s investments and strategies will involve exposure to foreign currencies. Currency risk is the risk that changes in the exchange rate between currencies will adversely affect the value (in U.S. dollar terms) of an investment. As long as the Fund holds a foreign security, its value will be affected by the value of the local currency relative to the U.S. dollar. When the Fund sells a foreign currency denominated security, its value may be worth less in U.S. dollars even if the security increases in value in its home country. U.S. dollar-denominated securities of foreign issuers may also be affected by currency risk, as the value of these securities may also be affected by changes in the issuer’s local currency. Additionally, and as a result of the Fund’s use of currency investment strategies, the Fund’s net currency positions may expose the Fund to losses independent of any securities positions. 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. 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. 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, fixed-income risk, and commodity-linked investments risk. Exchange-Traded Notes Risk. The Fund may invest in ETNs, which are debt securities whose returns are linked to a particular index. ETNs are typically linked to the performance of a commodities index that reflects the potential return on unleveraged investments in futures contracts of physical commodities, plus a specified rate of interest that could be earned on cash collateral. ETNs are subject to credit risk and counterparty risk. The value of an ETN may vary and may be influenced by time to maturity, level of supply and demand for the ETN, volatility and lack of liquidity in underlying commodities markets, changes in the applicable interest rates, changes in the issuer’s credit rating, and economic, legal, political, or geographic events that affect the referenced commodity. When the Fund invests in ETNs it will bear its proportionate share of any fees and expenses borne by the ETN. There may be restrictions on the Fund’s right to redeem its investment in an ETN, which is meant to be held until maturity. The Fund’s decision to sell its ETN holdings may be limited by the availability of a secondary market. Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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 will be 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 Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.44%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.42%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.69%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.09%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.60%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class A Shares
1 Year	rr_ExpenseExampleYear01	737
3 Years	rr_ExpenseExampleYear03	1,077
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class A Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	737
3 Years	rr_ExpenseExampleNoRedemptionYear03	1,077
Janus Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.56%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.54%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.56%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.14%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	2.42%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class C Shares
1 Year	rr_ExpenseExampleYear01	359
3 Years	rr_ExpenseExampleYear03	796
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class C Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	259
3 Years	rr_ExpenseExampleNoRedemptionYear03	796
Janus Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.55%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.53%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.80%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.05%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.75%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class S Shares
1 Year	rr_ExpenseExampleYear01	183
3 Years	rr_ExpenseExampleYear03	566
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class S Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	183
3 Years	rr_ExpenseExampleNoRedemptionYear03	566
Janus Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.37%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.35%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.37%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.07%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.30%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class I Shares
1 Year	rr_ExpenseExampleYear01	139
3 Years	rr_ExpenseExampleYear03	434
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class I Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	139
3 Years	rr_ExpenseExampleNoRedemptionYear03	434
Janus Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.30%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.28%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.30%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.05%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.25%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class N Shares
1 Year	rr_ExpenseExampleYear01	132
3 Years	rr_ExpenseExampleYear03	412
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class N Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	132
3 Years	rr_ExpenseExampleNoRedemptionYear03	412
Janus Diversified Alternatives 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 of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.55%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.53%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.55%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.05%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.50%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class T Shares
1 Year	rr_ExpenseExampleYear01	158
3 Years	rr_ExpenseExampleYear03	490
Expense Example, No Redemption, By Year, Column [Text]	rr_ExpenseExampleNoRedemptionByYearColumnName	Class T Shares
1 Year	rr_ExpenseExampleNoRedemptionYear01	158
3 Years	rr_ExpenseExampleNoRedemptionYear03	490

[1] The Fund may invest in commodity-linked investments through a wholly-owned subsidiary of the Fund that invests in commodity-linked investments. Janus Capital has contractually agreed that to the extent the Fund invests in the subsidiary, it shall not collect advisory fees from the Fund in an amount equal to the fee it collects from the subsidiary. The management fee waiver arrangement may not be discontinued by Janus Capital as long as its contract with the subsidiary is in place.

[2] Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.

[3] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses, which include the other expenses of the subsidiary shown above (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; brokerage commissions; interest; dividends; taxes; acquired fund fees and expenses; and extraordinary expenses) to 1.25% until at least November 1, 2014. 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 (December 28, 2012) 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.

XML

Document and Entity Information	12 Months Ended
	Dec. 28, 2012
Risk/Return:
Document Type	485BPOS
Document Period End Date	Dec. 28, 2012
Registrant Name	JANUS INVESTMENT FUND
Central Index Key	0000277751
Amendment Flag	false
Document Creation Date	Dec. 28, 2012
Document Effective Date	Dec. 28, 2012
Prospectus Date	Dec. 28, 2012

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Prospectus Date	rr_ProspectusDate	Dec. 28, 2012
Document Creation Date	dei_DocumentCreationDate	Dec. 28, 2012

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Prospectus Date	rr_ProspectusDate	Dec. 28, 2012
Janus Diversified Alternatives Fund | Class D Shares
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	FUND SUMMARY Janus Diversified Alternatives Fund
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Janus Diversified Alternatives Fund seeks absolute return with low correlation to stocks and bonds.
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.
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, 2014
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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.
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, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses without waivers 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.
Strategy [Heading]	rr_StrategyHeading	PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal market conditions, the Fund pursues its investment objective by investing in a diverse group of return drivers, each a type of risk premium (collectively, “risk premia”), across equity, fixed income, commodity, and currency asset classes. Risk premia refers to the return that is expected for assuming a particular market risk. For example, investors expect a higher return in exchange for the perceived risks associated with investing in emerging markets as compared to investing in developed markets. Accordingly, a belief that emerging market equities may outperform developed market equities presents a risk premia opportunity. The Fund seeks to generate returns by identifying and isolating diverse sources of potential risk premia, and combining these individual risk premia into a liquid portfolio that delivers consistent, absolute returns with a low correlation to the returns generated by investments in stocks and bonds. The Fund employs a proprietary multi-factor process to allocate the Fund’s assets across the various risk premia. The process begins with an approximate equal-weighted risk to each risk premia in which the Fund invests, so that no individual risk premia contributes disproportionately to the Fund’s risk profile and expected returns over the long term. Next, the Fund applies additional advanced allocation methodologies to the portfolio to tactically adjust the weights of individual risk premia. The risk premia allocations are rebalanced from time to time, and depending on market conditions and the portfolio managers’ beliefs regarding the expected returns, relative risk and correlation properties of one or more individual risk premia, the Fund may not utilize all identified risk premia in its investment process at all times. Janus Capital believes that this allocation process may provide better risk adjusted returns than a traditional asset allocation strategy that employs fixed weights for asset classes. The Fund employs various strategies within the equity, fixed income, commodity, and currency asset classes to identify risk premia and generate returns, including, but not limited to, relative value, momentum, credit, size, roll yield, systematic, and currency carry. Relative Value – Relative Value investing seeks to capture the spread between a relatively undervalued asset and a more expensive one. For example, one pool of equities often outperforms another pool of equities in a different sector or investment style. Relative value attempts to identify the difference in valuation associated with those assets and favors investments in the relatively undervalued pool to generate return. Momentum – Momentum investing seeks to capitalize on the expected continuance of trends in the market. For example, if interest rates are increasing, a momentum investor would invest in securities that would generate positive returns if rates continue to increase in the near term. Credit – Credit investing seeks to invest in fixed-income securities to realize the additional rate of return that corporate debt provides as compared to U.S. Treasuries. Size – Size investing seeks to generate returns by investing in small capitalization equity securities over large capitalization equity securities. The basis for this strategy is that over time, less liquid equities (small capitalization) will outperform more liquid equities (large capitalization). Roll Yield – Roll Yield investing seeks to capture returns from favoring certain maturities of commodity futures contracts over others. This strategy typically combines offsetting long and short exposures on various sets of individual commodity futures contracts that have different expiration dates. Systematic – Systematic investing seeks to invest in one or more asset classes, or a subset of a specific asset class, to generate the associated market return. For example, the Fund may invest a portion of the portfolio in global equities to generate the market returns associated with that type of investment. Currency Carry – Currency Carry investing seeks to generate returns by investing in higher yielding currencies versus lower yielding currencies. In a carry trade, low interest rate currencies may be sold, and high interest rate currencies may be purchased. As part of the process to identify and isolate specific risk premia and generate returns, the Fund may have both long and short exposure to securities in which it invests with respect to a risk premia. The Fund’s exposure to U.S. and non-U.S. investments, which may include emerging markets, will vary based on perceived investment opportunities and the portfolio managers’ global investment outlook. The Fund will make significant use of derivative instruments, 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. Derivatives will be used to gain exposure to the various asset classes in which the Fund may invest, to generate returns, for hedging purposes (to offset risks associated with an investment, currency exposure, or market conditions), to adjust currency exposure relative to a benchmark index, and to earn income and enhance returns. The Fund may utilize swaps, including equity, interest rate, currency, and total return swaps. The Fund may utilize options and futures, including forward commodity and currency contracts and U.S. Treasury, interest rate, and market index futures. The Fund’s use of options includes options purchased and sold (written). The Fund’s exposure to derivatives will vary and is not limited to those derivatives listed. 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, when available. The Fund’s exposure to derivatives will create a leveraging effect on the portfolio where market exposure exceeds amounts invested. This leverage will vary over time and may at times be significant. The Fund may have a substantial cash position due to margin and collateral requirements related to the Fund’s use of derivatives. Such margin and collateral requirements may limit the Fund’s ability to take advantage of other investment opportunities and may negatively affect the Fund’s ability to achieve its investment objective. The Fund’s equity and fixed-income exposure may be obtained through direct investment in equity and fixed-income securities or through investment in other Janus mutual funds, unaffiliated mutual funds, or exchange-traded funds (“ETFs”). The Fund may also utilize exchange-traded notes (“ETNs”). The equity securities or underlying equity funds in which the Fund invests may involve exposure to common stocks of companies of any size located anywhere in the world, from larger, well-established companies to smaller, emerging growth companies. The fixed-income securities or underlying fixed-income funds in which the Fund invests may include securities of any maturity and of any credit quality, and may include exposure to government bonds, corporate bonds, convertible bonds, mortgage-backed securities, zero-coupon bonds, and high-yield/high-risk bonds, also known as “junk” bonds. The Fund’s investment in ETFs and ETNs may be used to gain exposure to market indices, a basket of securities, commodities, currencies, or a particular commodity or currency. The Fund’s exposure to the commodity markets, in whole or in part, may be made through investment in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”), which is generally subject to the same investment policies and restrictions as the Fund. The Subsidiary will invest in commodity-related derivatives such as futures and swaps, ETNs, and other investments such as cash or U.S. Treasuries which may serve as margin or collateral for the Subsidiary’s commodity-linked derivative positions. Due to the nature of the investment process and the types of securities in which the Fund may invest, it may have high portfolio turnover compared to other funds.
Risk [Heading]	rr_RiskHeading	PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking a portfolio which includes exposure to equity (such as stocks or any other security representing an ownership interest), fixed-income (such as bonds, notes, and debentures), commodities, and currency asset classes, and which involves the use of derivatives. Such investments, and derivatives in particular, tend to be more volatile than many other investment choices. Management Risk. The Fund’s ability to achieve its investment objective depends largely upon the portfolio managers’ successful evaluation of the risks, potential returns, and correlation properties with respect to the various risk premia in which the Fund invests. There is a risk that the returns provided by individual risk premia may be subject to high volatility and that the portfolio managers’ beliefs about the risk, expected returns and correlation properties of one or more individual risk premia may be incorrect. Further, the Fund’s ability to achieve its investment objective also depends on the successful allocation of the Fund’s assets among various risk premia and asset classes, and you could lose money on your investment in the Fund as a result of these allocations. There is also a risk that the Fund’s investments will correlate with the performance of stocks and bonds to a greater degree than anticipated, and the Fund will not meet its investment objective. Finally, Janus Capital does not have prior experience managing a risk premia investment strategy, and there is no guarantee that the investment techniques and analysis used by the Fund’s portfolio managers will produce the desired results. Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual investment, or multiple investments, in the portfolio decreases at the same time. Further, while the Fund’s goal is to produce returns that have a low correlation to the stock and bond markets, you should understand that regardless of how well the Fund’s individual investments perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. The value of your investment in the Fund may fall, sometimes sharply, in response to changes in the market, and you could lose money. Because the Fund seeks to produce returns that have a low correlation to the returns generated by the stock and bond markets, the Fund may underperform these markets when these markets rise sharply or experience prolonged periods of outperformance. Additionally, the Fund’s performance may be negatively affected during prolonged periods when the returns provided by the risk premia are consistently low. 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. 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, short sales, 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. Short Sales Risk. Short sales are speculative transactions and involve special risks, including a greater reliance on the portfolio managers’ ability to accurately anticipate the future value of a security. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. The Fund’s losses are potentially unlimited in a short sale transaction. The use of short sales may also cause the Fund to have higher expenses than those of other funds. In addition, due to the investment process of long and short positions, the Fund may be subject to additional transaction costs that may lower the Fund’s returns. The Fund’s use of short sales may also have a leveraging effect on the Fund’s portfolio. 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. Commodity-Linked Investments Risk. The Fund may invest, directly or indirectly, 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. Subsidiary Risk. By investing in the Subsidiary, the Fund will be indirectly exposed to the risks associated with the Subsidiary’s investments, which are generally similar to those that are permitted to be held by the Fund. The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the “1940 Act”), and is not subject to all of the provisions of the 1940 Act. The Internal Revenue Service (“IRS”) has previously issued a number of private letter rulings to mutual funds (but not the Fund), which indicate that income from a fund’s investment in a wholly-owned foreign subsidiary that invests in commodity-linked derivatives, such as the Subsidiary, constitutes qualifying income. Changes in the laws of the United States and/or the Cayman Islands could result in the inability of the Fund and/or the Subsidiary to operate as described in the Fund’s Prospectus and the Statement of Additional Information. Such changes could adversely affect the Fund’s ability to meet its investment objective and jeopardize the Fund’s status as a regulated investment company under the U.S. tax code, which in turn may subject the Fund to higher tax rates and/or penalties. Foreign Exposure Risk. The Fund normally has 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 or an underlying mutual fund or ETF 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 exposure to emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries. Emerging Markets Risk. The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, seizure, nationalization, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve other risks. 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. Fixed-Income Securities Risk. The Fund may invest in a variety of fixed-income securities, either directly or indirectly through underlying mutual funds and ETFs. 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. Currency Risk. The Fund’s investments and strategies will involve exposure to foreign currencies. Currency risk is the risk that changes in the exchange rate between currencies will adversely affect the value (in U.S. dollar terms) of an investment. As long as the Fund holds a foreign security, its value will be affected by the value of the local currency relative to the U.S. dollar. When the Fund sells a foreign currency denominated security, its value may be worth less in U.S. dollars even if the security increases in value in its home country. U.S. dollar-denominated securities of foreign issuers may also be affected by currency risk, as the value of these securities may also be affected by changes in the issuer’s local currency. Additionally, and as a result of the Fund’s use of currency investment strategies, the Fund’s net currency positions may expose the Fund to losses independent of any securities positions. 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. 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. 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, fixed-income risk, and commodity-linked investments risk. Exchange-Traded Notes Risk. The Fund may invest in ETNs, which are debt securities whose returns are linked to a particular index. ETNs are typically linked to the performance of a commodities index that reflects the potential return on unleveraged investments in futures contracts of physical commodities, plus a specified rate of interest that could be earned on cash collateral. ETNs are subject to credit risk and counterparty risk. The value of an ETN may vary and may be influenced by time to maturity, level of supply and demand for the ETN, volatility and lack of liquidity in underlying commodities markets, changes in the applicable interest rates, changes in the issuer’s credit rating, and economic, legal, political, or geographic events that affect the referenced commodity. When the Fund invests in ETNs it will bear its proportionate share of any fees and expenses borne by the ETN. There may be restrictions on the Fund’s right to redeem its investment in an ETN, which is meant to be held until maturity. The Fund’s decision to sell its ETN holdings may be limited by the availability of a secondary market. Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Nondiversification Risk. Although the Fund seeks diverse sources of potential return or risk premia, the Fund is classified as nondiversified under the 1940 Act. 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 will be 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 Diversified Alternatives Fund | Class D Shares | Class D
Risk/Return:	rr_RiskReturnAbstract
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	Class D
Management Fees of the Fund and the Subsidiary	rr_ManagementFeesOverAssets	1.00%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.57%	[2]
Other Expenses of the Fund	rr_Component1OtherExpensesOverAssets	0.55%
Other Expenses of the Subsidiary	rr_Component2OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.57%	[3]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.19%	[3]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.38%	[3]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class D Shares
1 Year	rr_ExpenseExampleYear01	160
3 Years	rr_ExpenseExampleYear03	496

[1] The Fund may invest in commodity-linked investments through a wholly-owned subsidiary of the Fund that invests in commodity-linked investments. Janus Capital has contractually agreed that to the extent the Fund invests in the subsidiary, it shall not collect advisory fees from the Fund in an amount equal to the fee it collects from the subsidiary. The management fee waiver arrangement may not be discontinued by Janus Capital as long as its contract with the subsidiary is in place.

[2] Since the Fund is new, Other Expenses are based on the estimated expenses that the Fund expects to incur in its initial fiscal period.

[3] Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses, which include the other expenses of the subsidiary shown above (excluding administrative services fees payable pursuant to the Transfer Agency Agreement, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) to 1.25% until at least November 1, 2014. 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 (December 28, 2012) 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.