2.2.0.25truefalse0100035 - Document - Risk/Return Summary - Janus Long/Short Fund (Class A, C, S, I, R & T Shares) {Unlabeled}falsefalsetrue1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Janus Long/Short Fund [Member] {dei_LegalEntityAxis} : Alternative - Class A, C, S, I, R and T Shares [Member] 1/29/2010 - 1/28/2011 USD ($) $TwelveMonthsEnded_28Jan2011_Prospectus_Eight_Member_S000025891_Memberhttp://www.sec.gov/CIK0000277751duration2010-01-29T00:00:002011-01-28T00:00:00falsefalsejif277751_S000025891Memberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsejif277751_ProspectusEightMemberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$1false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://janus.com/role/riskreturnsummaryjanuslongshortfund1falsefalsefalse00Janus Long/Short Fund [Member] | Alternative - Class A, C, S, I, R and T Shares [Member]Janus Long/Short Fund [Member] | Alternative - Class A, C, S, I, R and T Shares [Member]falsefalsefalsefalsefalse1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Janus Long/Short Fund [Member] {dei_LegalEntityAxis} : Alternative - Class A, C, S, I, R and T Shares [Member] 1/29/2010 - 1/28/2011 USD ($) $TwelveMonthsEnded_28Jan2011_Prospectus_Eight_Member_S000025891_Memberhttp://www.sec.gov/CIK0000277751duration2010-01-29T00:00:002011-01-28T00:00:00falsefalsejif277751_S000025891Memberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsejif277751_ProspectusEightMemberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseJanus Long/Short Fund [Member] | Alternative - Class A, C, S, I, R and T Shares [Member]3false0rr_RiskReturnHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00FUND SUMMARY Janus Long/Short FundfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicatedReference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 falsefalseRisk/Return [Heading]4false0rr_ObjectiveHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00INVESTMENT OBJECTIVEfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective [Heading]5false0rr_ObjectivePrimaryTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Janus Long/Short Fund seeks long-term capital appreciation with an emphasis on absolute returns.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective, Primary [Text Block]6false0rr_ExpenseHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00FEES AND EXPENSES OF THE FUNDfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example This 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 then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. 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 may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph d -Subsection instructions falsefalseExpense [Heading]7false0rr_ExpenseNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00This 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.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown.The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense Narrative [Text Block]8false0rr_ExpenseBreakpointDiscountsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00For Class&#160;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 &#8220;Purchases&#8221; section on page&#160;31 of the Fund&#8217;s Prospectus and in the &#8220;Purchases&#8221; section on page&#160;85 of the Fund&#8217;s Statement of Additional Information.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInclude the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown.The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense Breakpoint Discounts [Text]9false0rr_ExpenseBreakpointMinimumInvestmentRequiredAmountrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse5000050000falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents the minimum level of investment required to qualify for discounted sales charges or fund expenses (SEC Form N-1A 2006-09-14 A.3.instructions.1.b).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense Breakpoint, Minimum Investment Required [Amount]10false0rr_ShareholderFeesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00SHAREHOLDER FEES (fees paid directly from your investment)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subsection table falsefalseShareholder Fees Caption [Text]11false0rr_ShareholderFeesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://janus.com/role/ShareholderFeesJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://janus.com/role/ShareholderFeesJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsehttp://janus.com/role/ShareholderFeesJanusLongShortFundfalsefalse0200135 - Schedule - Shareholder Fees - Janus Long/Short Fund (Class A, C, S, I & T Shares)truefalsefalse1falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass A, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077609Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class A, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass C, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077610Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class C, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass S, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077607Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class S, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$4falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass I, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077611Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class I, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$5falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass R, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077612Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class R, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$6falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass T, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077608Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class T, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*4false0rr_ShareholderFeesColumnNamerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;Afalsefalsefalsetruefalse2falsefalsefalse00Class&#160;Cfalsefalsefalsetruefalse3falsefalsefalse00Class Sfalsefalsefalsetruefalse4falsefalsefalse00Class Ifalsefalsefalsetruefalse5falsefalsefalse00Class Rfalsefalsefalsetruefalse6falsefalsefalse00Class TfalsefalsefalsetruefalseOtherus-types:textBlockItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subsection table falsefalseShareholder Fees Column [Text]0rr_ShareholderFeesColumnNametruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;AClass&#160;Afalsefalsefalsetruefalse2falsefalsefalse00Class&#160;CClass&#160;Cfalsefalsefalsetruefalse3falsefalsefalse00Class SClass Sfalsefalsefalsetruefalse4falsefalsefalse00Class IClass Ifalsefalsefalsetruefalse5falsefalsefalse00Class RClass Rfalsefalsefalsetruefalse6falsefalsefalse00Class TClass TfalsefalsefalsetruefalseOthernanafalsefalseShareholder Fees Column [Text]2falseRowprimaryElement*5false0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.05750.0575falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00000.0000falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection table falsefalseMaximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.05750.0575falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00000.0000falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseMaximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)3falseRowprimaryElement*6false0rr_MaximumDeferredSalesChargeOverOtherrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.00000.0000falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00000.0000falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph a -Clause i -Subsection instructions falsefalseMaximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)0rr_MaximumDeferredSalesChargeOverOthertruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00000.0000falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00000.0000falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseMaximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)4falseRowprimaryElement*7false0rr_RedemptionFeeOverRedemptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truetruetrue0.00000.0000falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.02000.0200falsefalsefalsetruefalse4truetruetrue0.02000.0200falsefalsefalsetruefalse5truetruetrue0.02000.0200falsefalsefalsetruefalse6truetruetrue0.02000.0200falsefalsefalsetruefalseOtherrr:NonPositivePure4Typepure"Redemption Fee" (as a percentage of amount redeemed, if applicable) If the Fund is an Exchange-Traded Fund and issues or redeems shares in creation units of not less than 25,000 shares each, exclude any fees charged for the purchase and redemption of the Fund's creation units. "Redemption Fee" includes a fee charged for any redemption of the Fund's shares, but does not include a deferred sales charge (load) imposed upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph b -Subsection instructions falsefalseRedemption fee on Shares held for 90 days or less (as a percentage of amount redeemed)0rr_RedemptionFeeOverRedemptiontruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00000.0000falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.02000.0200falsefalsefalsetruefalse4truetruetrue0.02000.0200falsefalsefalsetruefalse5truetruetrue0.02000.0200falsefalsefalsetruefalse6truetruetrue0.02000.0200falsefalsefalsetruefalseOthernanafalsefalseRedemption fee on Shares held for 90 days or less (as a percentage of amount redeemed)64Shareholder Fees - Janus Long/Short Fund (Class A, C, S, I & T Shares) Janus Long/Short Fund [Member] Alternative - Class A, C, S, I, R and T Shares [Member]UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ShareholderFeesData.No authoritative reference available.falsefalseShareholder Fees [Table]12false0rr_OperatingExpensesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringAnnual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 7 -Subsection table falsefalseOperating Expenses Caption [Text]13false0rr_AnnualFundOperatingExpensesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://janus.com/role/AnnualFundOperatingExpensesJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row rr_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://janus.com/role/AnnualFundOperatingExpensesJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row rr_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsehttp://janus.com/role/AnnualFundOperatingExpensesJanusLongShortFundfalsefalse0200235 - Schedule - Annual Fund Operating Expenses - Janus Long/Short Fund (Class A, C, S, I & T Shares)truefalsefalse1falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass A, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077609Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class A, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass C, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077610Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class C, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass S, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077607Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class S, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$4falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass I, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077611Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class I, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$5falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass R, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077612Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class R, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$6falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass T, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077608Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class T, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*4false0rr_OperatingExpensesColumnNamerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;Afalsefalsefalsetruefalse2falsefalsefalse00Class&#160;Cfalsefalsefalsetruefalse3falsefalsefalse00Class Sfalsefalsefalsetruefalse4falsefalsefalse00Class Ifalsefalsefalsetruefalse5falsefalsefalse00Class Rfalsefalsefalsetruefalse6falsefalsefalse00Class TfalsefalsefalsetruefalseOtherus-types:textBlockItemTypestringAnnual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 7 -Subsection table falsefalseOperating Expenses Column [Text]0rr_OperatingExpensesColumnNametruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;AClass&#160;Afalsefalsefalsetruefalse2falsefalsefalse00Class&#160;CClass&#160;Cfalsefalsefalsetruefalse3falsefalsefalse00Class SClass Sfalsefalsefalsetruefalse4falsefalsefalse00Class IClass Ifalsefalsefalsetruefalse5falsefalsefalse00Class RClass Rfalsefalsefalsetruefalse6falsefalsefalse00Class TClass TfalsefalsefalsetruefalseOthernanafalsefalseOperating Expenses Column [Text]2falseRowprimaryElement*5false0rr_ManagementFeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.01250.0125falsefalsefalsetruefalse2truetruetrue0.01250.0125falsefalsefalsetruefalse3truetruetrue0.01250.0125falsefalsefalsetruefalse4truetruetrue0.01250.0125falsefalsefalsetruefalse5truetruetrue0.01250.0125falsefalsefalsetruefalse6truetruetrue0.01250.0125falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph a -Subsection instructions falsefalseManagement Fees0rr_ManagementFeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01250.0125falsefalsefalsetruefalse2truetruetrue0.01250.0125falsefalsefalsetruefalse3truetruetrue0.01250.0125falsefalsefalsetruefalse4truetruetrue0.01250.0125falsefalsefalsetruefalse5truetruetrue0.01250.0125falsefalsefalsetruefalse6truetruetrue0.01250.0125falsefalsefalsetruefalseOthernanafalsefalseManagement Fees3falseRowprimaryElement*6false0rr_DistributionAndService12b1FeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.00250.0025falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00500.0050falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 9 -Subsection table falsefalseDistribution/Service (12b-1) Fees0rr_DistributionAndService12b1FeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.00250.0025falsefalsefalsetruefalse4truetruetrue0.00000.0000falsefalsefalsetruefalse5truetruetrue0.00500.0050falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseDistribution/Service (12b-1) Fees4falseRowprimaryElement*7false0rr_OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.02950.0295falsefalsefalsetruefalse2truetruetrue0.02460.0246falsefalsefalsetruefalse3truetruetrue0.02510.0251falsefalsefalsetruefalse4truetruetrue0.02430.0243falsefalsefalsetruefalse5truetruetrue0.02510.0251falsefalsefalsetruefalse6truetruetrue0.02500.0250falsefalsefalsetruefalseOtherrr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause i -Subsection instructions falsefalseOther Expenses0rr_OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.02950.0295falsefalsefalsetruefalse2truetruetrue0.02460.0246falsefalsefalsetruefalse3truetruetrue0.02510.0251falsefalsefalsetruefalse4truetruetrue0.02430.0243falsefalsefalsetruefalse5truetruetrue0.02510.0251falsefalsefalsetruefalse6truetruetrue0.02500.0250falsefalsefalsetruefalseOthernanafalsefalseOther Expenses5falseRowprimaryElement*8false0rr_Component2OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.01030.0103falsefalsefalsetruefalse2truetruetrue0.00540.0054falsefalsefalsetruefalse3truetruetrue0.00590.0059falsefalsefalsetruefalse4truetruetrue0.00510.0051falsefalsefalsetruefalse5truetruetrue0.00590.0059falsefalsefalsetruefalse6truetruetrue0.00580.0058falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureThe Fund may subdivide this caption into no more than three subcaptions that identify the largest expense or expenses comprising "Other Expenses," but must include a total of all "Other Expenses." Alternatively, the Fund may include the components of "Other Expenses" in a parenthetical to the caption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 10 -Subsection table falsefalseRemaining Other Expenses0rr_Component2OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01030.0103falsefalsefalsetruefalse2truetruetrue0.00540.0054falsefalsefalsetruefalse3truetruetrue0.00590.0059falsefalsefalsetruefalse4truetruetrue0.00510.0051falsefalsefalsetruefalse5truetruetrue0.00590.0059falsefalsefalsetruefalse6truetruetrue0.00580.0058falsefalsefalsetruefalseOthernanafalsefalseRemaining Other Expenses6falseRowprimaryElement*9false0rr_Component1OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.01920.0192falsefalsefalsetruefalse2truetruetrue0.01920.0192falsefalsefalsetruefalse3truetruetrue0.01920.0192falsefalsefalsetruefalse4truetruetrue0.01920.0192falsefalsefalsetruefalse5truetruetrue0.01920.0192falsefalsefalsetruefalse6truetruetrue0.01920.0192falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureThe Fund may subdivide this caption into no more than three subcaptions that identify the largest expense or expenses comprising "Other Expenses," but must include a total of all "Other Expenses." Alternatively, the Fund may include the components of "Other Expenses" in a parenthetical to the caption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause iii -Subsection instructions falsefalseShort Sale Dividend Expenses0rr_Component1OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01920.0192falsefalsefalsetruefalse2truetruetrue0.01920.0192falsefalsefalsetruefalse3truetruetrue0.01920.0192falsefalsefalsetruefalse4truetruetrue0.01920.0192falsefalsefalsetruefalse5truetruetrue0.01920.0192falsefalsefalsetruefalse6truetruetrue0.01920.0192falsefalsefalsetruefalseOthernanafalsefalseShort Sale Dividend Expenses7falseRowprimaryElement*10false0rr_AcquiredFundFeesAndExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.00020.0002[1]falsefalsefalsetruefalse2truetruetrue0.00020.0002[1]falsefalsefalsetruefalse3truetruetrue0.00020.0002[1]falsefalsefalsetruefalse4truetruetrue0.00020.0002[1]falsefalsefalsetruefalse5truetruetrue0.00020.0002[1]falsefalsefalsetruefalse6truetruetrue0.00020.0002[1]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseAcquired Fund Fees and Expenses0rr_AcquiredFundFeesAndExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1]1truetruetrue0.00020.0002falsefalsefalsetruefalse2truetruetrue0.00020.0002falsefalsefalsetruefalse3truetruetrue0.00020.0002falsefalsefalsetruefalse4truetruetrue0.00020.0002falsefalsefalsetruefalse5truetruetrue0.00020.0002falsefalsefalsetruefalse6truetruetrue0.00020.0002falsefalsefalsetruefalseOthernanafalsefalseAcquired Fund Fees and Expenses8falseRowprimaryElement*11false0rr_ExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.04470.0447[2]falsefalsefalsetruefalse2truetruetrue0.04730.0473[2]falsefalsefalsetruefalse3truetruetrue0.04030.0403[2]falsefalsefalsetruefalse4truetruetrue0.0370.037[2]falsefalsefalsetruefalse5truetruetrue0.04280.0428[2]falsefalsefalsetruefalse6truetruetrue0.03770.0377[2]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph d -Subsection instructions falsefalseTotal Annual Fund Operating Expenses0rr_ExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.04470.0447falsefalsefalsetruefalse2truetruetrue0.04730.0473falsefalsefalsetruefalse3truetruetrue0.04030.0403falsefalsefalsetruefalse4truetruetrue0.0370.037falsefalsefalsetruefalse5truetruetrue0.04280.0428falsefalsefalsetruefalse6truetruetrue0.03770.0377falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses9falseRowprimaryElement*12false0rr_FeeWaiverOrReimbursementOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truetruetrue0.00530.0053[2]falsefalsefalsetruefalse2truetruetrue0.00040.0004[2]falsefalsefalsetruefalse3truetruetrue0.00000.0000[2]falsefalsefalsetruefalse4truetruetrue0.00020.0002[2]falsefalsefalsetruefalse5truetruetrue0.00000.0000[2]falsefalsefalsetruefalse6truetruetrue0.00000.0000[2]falsefalsefalsetruefalseOtherrr:NonPositivePure4TypepureTotal Annual Fund Operating Expenses. If there were expense reimbursement or fee waiver arrangements that reduced any Fund operating expenses and will continue to reduce them for no less than one year from the effective date of the Fund's registration statement, a Fund may add two captions to the table one caption showing the amount of the expense reimbursement or fee waiver, and a second caption showing the Fund's net expenses after subtracting the fee reimbursement or expense waiver from the total fund operating expenses. The Fund should place these additional captions directly below the "Total Annual Fund Operating Expenses" caption of the table and should use appropriate descriptive captions, such as "Fee Waiver [and/or Expense Reimbursement]" and "Total Annual Fund Operating Expenses After Fee Waiver [and/or Expense Reimbursement]," respectively. If the Fund provides this disclosure, also disclose the period for which the expense reimbursement or fee waiver arrangement is expected to continue, and briefly describe who can terminate the arrangement and under what circumstances.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseFee Waiver0rr_FeeWaiverOrReimbursementOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.00530.0053falsefalsefalsetruefalse2truetruetrue0.00040.0004falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalse4truetruetrue0.00020.0002falsefalsefalsetruefalse5truetruetrue0.00000.0000falsefalsefalsetruefalse6truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseFee Waiver10falseRowprimaryElement*13false0rr_NetExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.03940.0394[2]falsefalsefalsetruefalse2truetruetrue0.04690.0469[2]falsefalsefalsetruefalse3truetruetrue0.04030.0403[2]falsefalsefalsetruefalse4truetruetrue0.03680.0368[2]falsefalsefalsetruefalse5truetruetrue0.04280.0428[2]falsefalsefalsetruefalse6truetruetrue0.03770.0377[2]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseNet Annual Fund Operating Expenses After Fee Waiver0rr_NetExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.03940.0394falsefalsefalsetruefalse2truetruetrue0.04690.0469falsefalsefalsetruefalse3truetruetrue0.04030.0403falsefalsefalsetruefalse4truetruetrue0.03680.0368falsefalsefalsetruefalse5truetruetrue0.04280.0428falsefalsefalsetruefalse6truetruetrue0.03770.0377falsefalsefalsetruefalseOthernanafalsefalseNet Annual Fund Operating Expenses After Fee Waiver1"Acquired Fund" refers to any underlying fund (including, but not limited to, exchange-traded funds) in which a fund invests or has invested during the period. Acquired fund fees and expenses are indirect expenses a fund may incur as a result of investing in shares of an underlying fund. The Fund's "Total Annual Fund Operating Expenses" may not correlate to the "ratio of gross expenses to average net assets" presented in the Financial Highlights tables because that ratio includes only the direct operating expenses incurred by the Fund, not the indirect costs of investing in Acquired Funds.2Janus Capital has contractually agreed to waive the Fund's total annual fund operating expenses (excluding the distribution and shareholder servicing fees - applicable to Class A Shares, Class C Shares, Class S Shares, and Class R Shares; administrative services fees payable pursuant to the Transfer Agency Agreement - applicable to Class S Shares, Class R Shares, and Class T Shares; brokerage commissions, interest, dividends, taxes, and extraordinary expenses including, but not limited to, acquired fund fees and expenses) to 1.75% until at least February 1, 2012. The contractual waiver may be terminated or modified at any time prior to this date only at the discretion of the Board of Trustees.610Annual Fund Operating Expenses - Janus Long/Short Fund (Class A, C, S, I & T Shares) Janus Long/Short Fund [Member] Alternative - Class A, C, S, I, R and T Shares [Member]UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to OperatingExpensesData.No authoritative reference available.falsefalseAnnual Fund Operating Expenses [Table]14false0rr_ExpenseExampleHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00EXAMPLE:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringHeading for Expense Example.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalseExpense Example [Heading]15false0rr_ExpenseExampleNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The 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.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThe Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection example falsefalseExpense Example Narrative [Text Block]16false0rr_ExpenseExampleByYearHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The 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&#8217;s operating expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example by Year [Heading]17false0rr_ExpenseExampleByYearCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00If Shares are redeemed:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example by, Year, Caption [Text]18false0rr_ExpenseExampleWithRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;"&gt;~ http://janus.com/role/ExpenseExampleJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;"&gt;~ http://janus.com/role/ExpenseExampleJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>truehttp://janus.com/role/ExpenseExampleJanusLongShortFundfalsefalse0200335 - Schedule - Expense Example - Janus Long/Short Fund (Class A, C, S, I & T Shares) {Transposed}truefalsefalse1falseColumnprimaryElement*4false0rr_ExpenseExampleByYearColumnNamerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;A Sharesfalsefalsefalsetruefalse2falsefalsefalse00Class&#160;C Sharesfalsefalsefalsetruefalse3falsefalsefalse00Class&#160;S Sharesfalsefalsefalsetruefalse4falsefalsefalse00Class&#160;I Sharesfalsefalsefalsetruefalse5falsefalsefalse00Class&#160;R Sharesfalsefalsefalsetruefalse6falsefalsefalse00Class&#160;T SharesfalsefalsefalsetruefalseOtherus-types:textBlockItemTypestringThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example, By Year, Column [Text]falseUSDfalsefalse$2falseColumnprimaryElement*5false0rr_ExpenseExampleYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue997997falsefalsefalsetruefalse2truefalsetrue574574falsefalsefalsetruefalse3truefalsetrue405405falsefalsefalsetruefalse4truefalsetrue372372falsefalsefalsetruefalse5truefalsetrue430430falsefalsefalsetruefalse6truefalsetrue379379falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalse1 YearfalseUSDfalsefalse$3falseColumnprimaryElement*6false0rr_ExpenseExampleYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue18491849falsefalsefalsetruefalse2truefalsetrue14251425falsefalsefalsetruefalse3truefalsetrue12271227falsefalsefalsetruefalse4truefalsetrue11321132falsefalsefalsetruefalse5truefalsetrue12981298falsefalsefalsetruefalse6truefalsetrue11521152falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse3 YearsfalseUSDfalsefalse$4falseColumnprimaryElement*7false0rr_ExpenseExampleYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue27102710falsefalsefalsetruefalse2truefalsetrue23812381falsefalsefalsetruefalse3truefalsetrue20642064falsefalsefalsetruefalse4truefalsetrue19111911falsefalsefalsetruefalse5truefalsetrue21792179falsefalsefalsetruefalse6truefalsetrue19441944falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse5 YearsfalseUSDfalsefalse$5falseColumnprimaryElement*8false0rr_ExpenseExampleYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue49014901falsefalsefalsetruefalse2truefalsetrue47944794falsefalsefalsetruefalse3truefalsetrue42314231falsefalsefalsetruefalse4truefalsetrue39503950falsefalsefalsetruefalse5truefalsetrue44374437falsefalsefalsetruefalse6truefalsetrue40104010falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse10 YearsfalseUSDfalsefalse$1falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass A, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077609Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class A, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;A SharesClass&#160;A Sharesfalsefalsefalsetruefalse2truefalsetrue997997falsefalsefalsetruefalse3truefalsetrue18491849falsefalsefalsetruefalse4truefalsetrue27102710falsefalsefalsetruefalse5truefalsetrue49014901falsefalsefalsetruefalseOthernanafalsefalseClass A, Janus Long/Short Fund [Member]2falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass C, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077610Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class C, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;C SharesClass&#160;C Sharesfalsefalsefalsetruefalse2truefalsetrue574574falsefalsefalsetruefalse3truefalsetrue14251425falsefalsefalsetruefalse4truefalsetrue23812381falsefalsefalsetruefalse5truefalsetrue47944794falsefalsefalsetruefalseOthernanafalsefalseClass C, Janus Long/Short Fund [Member]3falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass S, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077607Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class S, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;S SharesClass&#160;S Sharesfalsefalsefalsetruefalse2truefalsetrue405405falsefalsefalsetruefalse3truefalsetrue12271227falsefalsefalsetruefalse4truefalsetrue20642064falsefalsefalsetruefalse5truefalsetrue42314231falsefalsefalsetruefalseOthernanafalsefalseClass S, Janus Long/Short Fund [Member]4falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass I, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077611Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class I, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;I SharesClass&#160;I Sharesfalsefalsefalsetruefalse2truefalsetrue372372falsefalsefalsetruefalse3truefalsetrue11321132falsefalsefalsetruefalse4truefalsetrue19111911falsefalsefalsetruefalse5truefalsetrue39503950falsefalsefalsetruefalseOthernanafalsefalseClass I, Janus Long/Short Fund [Member]5falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass R, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077612Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class R, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;R SharesClass&#160;R Sharesfalsefalsefalsetruefalse2truefalsetrue430430falsefalsefalsetruefalse3truefalsetrue12981298falsefalsefalsetruefalse4truefalsetrue21792179falsefalsefalsetruefalse5truefalsetrue44374437falsefalsefalsetruefalseOthernanafalsefalseClass R, Janus Long/Short Fund [Member]6falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass T, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077608Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class T, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;T SharesClass&#160;T Sharesfalsefalsefalsetruefalse2truefalsetrue379379falsefalsefalsetruefalse3truefalsetrue11521152falsefalsefalsetruefalse4truefalsetrue19441944falsefalsefalsetruefalse5truefalsetrue40104010falsefalsefalsetruefalseOthernanafalsefalseClass T, Janus Long/Short Fund [Member]56Expense Example - Janus Long/Short Fund (Class A, C, S, I & T Shares) Janus Long/Short Fund [Member] Alternative - Class A, C, S, I, R and T Shares [Member] (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnprimaryElement*RowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExample.No authoritative reference available.falsefalseExpense Example, With Redemption [Table]19false0rr_ExpenseExampleNoRedemptionByYearCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00If Shares are not redeemed:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalseExpense Example, No Redemption, By Year, Caption [Text]20false0rr_ExpenseExampleNoRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;"&gt;~ http://janus.com/role/ExpenseExampleNoRedemptionJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;"&gt;~ http://janus.com/role/ExpenseExampleNoRedemptionJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000025891_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>truehttp://janus.com/role/ExpenseExampleNoRedemptionJanusLongShortFundfalsefalse0200435 - Schedule - Expense Example, No Redemption - Janus Long/Short Fund (Class A, C, S, I & T Shares) {Transposed}truefalsefalse1falseColumnprimaryElement*4false0rr_ExpenseExampleNoRedemptionByYearColumnNamerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;A Sharesfalsefalsefalsetruefalse2falsefalsefalse00Class&#160;C Sharesfalsefalsefalsetruefalse3falsefalsefalse00Class&#160;S Sharesfalsefalsefalsetruefalse4falsefalsefalse00Class&#160;I Sharesfalsefalsefalsetruefalse5falsefalsefalse00Class&#160;R Sharesfalsefalsefalsetruefalse6falsefalsefalse00Class&#160;T SharesfalsefalsefalsetruefalseOtherus-types:textBlockItemTypestringYou would pay the following expenses if you did not redeem your shares.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalseExpense Example, No Redemption, By Year, Column [Text]falseUSDfalsefalse$2falseColumnprimaryElement*5false0rr_ExpenseExampleNoRedemptionYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue997997falsefalsefalsetruefalse2truefalsetrue474474falsefalsefalsetruefalse3truefalsetrue405405falsefalsefalsetruefalse4truefalsetrue372372falsefalsefalsetruefalse5truefalsetrue430430falsefalsefalsetruefalse6truefalsetrue379379falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalse1 YearfalseUSDfalsefalse$3falseColumnprimaryElement*6false0rr_ExpenseExampleNoRedemptionYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue18491849falsefalsefalsetruefalse2truefalsetrue14251425falsefalsefalsetruefalse3truefalsetrue12271227falsefalsefalsetruefalse4truefalsetrue11321132falsefalsefalsetruefalse5truefalsetrue12981298falsefalsefalsetruefalse6truefalsetrue11521152falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalse3 YearsfalseUSDfalsefalse$4falseColumnprimaryElement*7false0rr_ExpenseExampleNoRedemptionYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue27102710falsefalsefalsetruefalse2truefalsetrue23812381falsefalsefalsetruefalse3truefalsetrue20642064falsefalsefalsetruefalse4truefalsetrue19111911falsefalsefalsetruefalse5truefalsetrue21792179falsefalsefalsetruefalse6truefalsetrue19441944falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalse5 YearsfalseUSDfalsefalse$5falseColumnprimaryElement*8false0rr_ExpenseExampleNoRedemptionYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsetrue49014901falsefalsefalsetruefalse2truefalsetrue47944794falsefalsefalsetruefalse3truefalsetrue42314231falsefalsefalsetruefalse4truefalsetrue39503950falsefalsefalsetruefalse5truefalsetrue44374437falsefalsefalsetruefalse6truefalsetrue40104010falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalse10 YearsfalseUSDfalsefalse$1falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass A, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077609Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class A, Janus Long/Short Fund [Member]Alternative - 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Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class R, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;R SharesClass&#160;R Sharesfalsefalsefalsetruefalse2truefalsetrue430430falsefalsefalsetruefalse3truefalsetrue12981298falsefalsefalsetruefalse4truefalsetrue21792179falsefalsefalsetruefalse5truefalsetrue44374437falsefalsefalsetruefalseOthernanafalsefalseClass R, Janus Long/Short Fund [Member]6falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass T, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077608Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class T, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Class&#160;T SharesClass&#160;T Sharesfalsefalsefalsetruefalse2truefalsetrue379379falsefalsefalsetruefalse3truefalsetrue11521152falsefalsefalsetruefalse4truefalsetrue19441944falsefalsefalsetruefalse5truefalsetrue40104010falsefalsefalsetruefalseOthernanafalsefalseClass T, Janus Long/Short Fund [Member]56Expense Example, No Redemption - Janus Long/Short Fund (Class A, C, S, I & T Shares) Janus Long/Short Fund [Member] Alternative - Class A, C, S, I, R and T Shares [Member] (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnprimaryElement*RowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExampleNoRedemption.No authoritative reference available.falsefalseExpense Example, No Redemption [Table]21false0rr_PortfolioTurnoverHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Portfolio Turnover:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 5 -Subsection instructions falsefalsePortfolio Turnover [Heading]22false0rr_PortfolioTurnoverTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The Fund pays transaction costs, such as commissions, when it buys and sells securities (or &#8220;turns over&#8221; 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&#8217;s performance. During the most recent fiscal period, the Fund&#8217;s portfolio turnover rate was 140% of the average value of its portfolio.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subsection example falsefalsePortfolio Turnover [Text Block]23false0rr_PortfolioTurnoverRaterrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse1.401.40falsefalsefalsefalsefalseOtherxbrli:pureItemTypepureThis element represents the rate of portfolio turnover presented as a percentage (SEC Form N-1A 2006-09-14 A.3.example.3 Portfolio Turnover A.3.instructions.5 Portfolio Turnover).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subsection example falsefalsePortfolio Turnover, Rate24false0rr_StrategyHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00PRINCIPAL INVESTMENT STRATEGIESfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy [Heading]25false0rr_StrategyNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<p>Under normal circumstances, the Fund generally pursues its investment objective by taking both long and short positions in domestic and foreign equity securities, including those in emerging markets, and exchange-traded funds (&#8220;ETFs&#8221;) that invest primarily in equity securities. The Fund&#8217;s portfolio managers believe that a combination of long and short positions may provide positive returns regardless of market conditions through a complete market cycle and may offer reduced risk. The Fund will generally buy long securities that the portfolio managers believe will go up in price and will sell short ETFs and other equity securities the portfolio managers believe will go down in price. The Fund may, to a lesser degree, also take long and short positions in instruments that provide additional exposure to the equity markets, including options, futures, and other index-based instruments. The Fund&#8217;s investments may include holdings across different industries, sectors, and regions.</p><p>The allocation between long and short positions is a result of the portfolio managers&#8217; strategic investment process. The Fund does not intend to be market neutral and anticipates that it will generally hold a higher percentage of its assets in long positions than short positions (i.e., the Fund will be &#8220;net long&#8221;). The portfolio managers will manage the Fund&#8217;s net exposure between long and short positions and will determine that the Fund&#8217;s allocation be modified based on certain factors, including changes in market conditions.</p><p>In choosing long positions, the Fund&#8217;s portfolio managers look at companies individually to determine if a company is an attractive investment opportunity and if it is consistent with the Fund&#8217;s investment policies. The Fund&#8217;s portfolio managers emphasize long positions in companies with attractive price/free cash flow, which is the relationship between the price of a stock and the company&#8217;s available cash from operations, minus capital expenditures. The portfolio managers typically seek attractively valued companies that are improving their free cash flow and returns on invested capital, which also may include special situations companies that are experiencing management changes and/or are currently out of favor.</p><p>The Fund&#8217;s portfolio managers will generally target short positions in ETFs. The portfolio managers may also look at companies with unsustainable cash generation, poor capital structure, returns below their cost of capital, and share prices that reflect unrealistic expectations of the company&#8217;s future opportunities. The portfolio managers may deploy unique strategies when shorting ETFs and/or securities to minimize risk. For example, some investments may be held short to remove some of the market risk of a long position while accentuating the information advantage the portfolio managers believe they have in a long position in the portfolio. The Fund may invest in or short any type of ETF.</p><p>The Fund intends to also write (sell) covered call options on individual equity securities held long in an effort to generate income and to reduce the overall volatility of the Fund. A call option is &#8220;covered&#8221; when the Fund either holds the security subject to the option or an option to purchase the same security at an exercise price equal to or less than the exercise price of the covered call option. When the Fund writes a covered call option, the Fund makes an obligation to deliver the security at an agreed-upon strike price on or before a predetermined date in the future in return for a premium. The Fund may also engage in other types of options transactions in order to achieve its investment objective</p><p>In addition to taking short positions in ETFs, the Fund&#8217;s portfolio managers may also take short positions in other equity securities. In general, a short position is one where the Fund has sold at the current market price a security that it does not own in anticipation of a decline in the market value of the security. To complete a short sale, the Fund must borrow the security to make delivery to the buyer. The Fund then is obligated to replace the borrowed security by purchasing the security at the market price at the time of replacement. The price at such time may be more or less than the price at which the security was sold by the Fund. Until the borrowed security is replaced, the Fund is required to pay to the lender amounts equal to any dividends or interest that accrue during the period of the loan. To borrow the security, the Fund also may be required to pay a premium to the lender, which would increase the cost of the security sold. The proceeds of the short sale will be retained by the broker to the extent necessary to meet margin requirements, until the short position is closed.</p><p>Until the Fund closes its short position or replaces the borrowed security, the Fund will designate liquid assets it owns (other than the short sale proceeds) as segregated assets in an amount equal to its obligation to purchase the securities sold short, as required under the Investment Company Act of 1940, as amended (the &#8220;1940 Act&#8221;). The amount segregated in this manner will be increased or decreased each business day equal to the change in market value of the Fund&#8217;s obligation to purchase the security sold short. If the lending broker requires the Fund to deposit collateral (in addition to the short sales proceeds that the broker holds during the period of the short sale), which may be as much as 50% of the value of the securities sold short, the amount of the additional collateral may be deducted in determining the amount of cash or liquid assets the Fund is required to segregate to cover the short sale obligation pursuant to the 1940 Act. The amount segregated must be unencumbered by any other obligation or claim other than the obligation that is being covered. The Fund believes that short sale obligations that are covered, either by an offsetting asset or right (acquiring the security sold short or having an option to purchase the security sold short at exercise price that covers the obligation), or by the Fund&#8217;s segregated asset procedures (or a combination thereof), are not senior securities under the 1940 Act and are not subject to the Fund&#8217;s borrowing restrictions. This requirement to segregate assets limits the Fund&#8217;s leveraging of its investments and the related risk of losses from leveraging. The Fund also is required to pay the lender of the security any dividends or interest that accrues on a borrowed security during the period of the loan. Depending on the arrangements made with the broker or custodian, the Fund may or may not receive any payments (including interest) on collateral it has deposited with the broker.</p><p>The Fund may borrow money from banks to the extent permitted by the 1940 Act, including for investment purposes. Such borrowings may be on a secured or unsecured basis at fixed or variable rates of interest. The 1940 Act requires the Fund to maintain continuous asset coverage of not less than 300% with respect to all borrowings that are considered &#8220;senior securities&#8221; (generally borrowings other than for temporary or emergency purposes). This allows the Fund to borrow from banks up to 1/3 of its total assets (including the amount borrowed). If such asset coverage should decline to less than 300% due to market fluctuations or other reasons, the Fund may be required to dispose of some of its portfolio holdings within three days in order to reduce the Fund&#8217;s debt and restore the 300% asset coverage, even though it may be disadvantageous from an investment standpoint to dispose of assets at that time. The Fund&#8217;s short sales and related margin requirements may reduce the ability of the Fund to borrow money.</p><p> The Fund may also invest its assets in derivatives, which are instruments that have a value derived from an underlying asset, such as stocks, bonds, commodities, currencies, interest rates, or market indices, as substitutes for securities in which the Fund invests. The Fund has invested in and may continue to invest in derivative instruments (by taking long and/or short positions), including, but not limited to, put and call options, futures contracts, and forward currency contracts to increase or decrease the Fund&#8217;s exposure to a particular market, to manage or adjust the risk profile of the Fund, and to earn income and enhance returns. The Fund&#8217;s exposure to derivatives will vary, is not limited to those derivatives listed, and could be significant at times.</p>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy Narrative [Text Block]26false0rr_RiskHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00PRINCIPAL INVESTMENT RISKSfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subsection b falsefalseRisk [Heading]27false0rr_RiskNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<p>The biggest risk is that the Fund&#8217;s returns will vary, and you could lose money. The Fund invests primarily in common stocks, which tend to be more volatile than many other investment choices.</p><p><b><i>Long/Short Risk.</i></b> The value of the Fund&#8217;s long portfolio may decrease if the value of an individual company or multiple companies in the portfolio decreases or if the Fund&#8217;s portfolio managers are incorrect about their assessment of a company&#8217;s intrinsic worth. Further, regardless of how well individual companies perform, the value of the Fund&#8217;s long portfolio could also decrease if there are deteriorating economic or market conditions, including, but not limited to, a general decline in prices on the stock markets, a general decline in real estate markets, a decline in commodities prices, or if the market favors different types of securities than the types of securities in which the Fund invests. Conversely, the value of the Fund&#8217;s short positions may result in a loss (which may be unlimited) if the value of an individual company or multiple companies in the portfolio increases or if the stock market goes up, regardless of how well the businesses of individual companies in the portfolio perform. If the value of the Fund&#8217;s portfolio decreases, the Fund&#8217;s net asset value will also decrease, which means if you sell your shares in the Fund you may lose money.</p><p><b><i>Short Sales Risk.</i></b> Short sales are speculative transactions and involve special risks, including a greater reliance on the portfolio managers&#8217; 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&#8217;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&#8217;s returns. The Fund&#8217;s use of short sales may also have a leveraging effect on the Fund&#8217;s portfolio.</p><p><b><i>Foreign Exposure Risk.</i></b> The Fund may have significant exposure to foreign markets, including emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. 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&#8217;s performance than it would in a more geographically diversified portfolio. The Fund&#8217;s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.</p><p><b><i>Emerging Markets Risk.</i></b> The risks of foreign investing mentioned above are heightened when investing in emerging markets. Emerging markets securities are exposed to a number of additional risks, which may result from less government supervision and regulation of business and industry practices, 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. In addition, the Fund&#8217;s investments may be denominated in foreign currencies and therefore, changes in the value of a country&#8217;s currency compared to the U.S. dollar may affect the value of the Fund&#8217;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&#8217;s performance. Some of the risks of investing directly in foreign and emerging market securities may be reduced when the Fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve specialized risks. As of September 30, 2010, approximately 14.3% of the Fund&#8217;s investments in long positions were in emerging markets.</p><p><b><i>Exchange-Traded Funds Risk.</i></b> The Fund may invest in or short ETFs which are typically open-end investment companies that are traded on a national securities exchange. ETFs typically incur fees, such as investment advisory and other operating expenses that are separate from those of the Fund, which will be indirectly paid by the Fund. As a result, the cost of investing in the Fund may be higher than the cost of investing directly in ETFs and may be higher than other mutual funds that invest directly in stocks and bonds. Further, the price movement of an ETF may fluctuate against the underlying index it tracks and may result in a loss. Because the value of ETF shares depends on the demand in the market, the Fund may not be able to purchase or sell an ETF at the most optimal time, which could adversely affect the Fund&#8217;s performance.</p><p>The ETFs in which the Fund invests are subject to specific risks, depending on the investment strategy of the ETF. In turn, the Fund will be subject to substantially the same risks as those associated with direct exposure to the securities held by the ETF. Because the Fund may invest in a broad range of ETFs, such risks may include, but are not limited to, leverage risk, foreign exposure risk, and commodities risk. Similarly, short sales of ETF shares are speculative transactions and are subject to other specific risks. In addition, if the Fund sells short shares in ETFs that are financially leveraged, such short sales may be expected to exhibit enhanced volatility in market price as compared to short sales of shares of similar ETFs without a leveraged capital structure, which may negatively affect the Fund&#8217;s returns.</p><p><b><i>Options Writing Strategy Risk.</i></b> During periods in which the equity markets are generally unchanged or falling, a portfolio such as that held by the Fund which utilizes a covered call option writing strategy may outperform the same portfolio without a covered call option writing strategy because of the additional premiums received from writing covered call options. Similarly, in a modestly rising market, the Fund may also outperform the same portfolio without a covered call option writing strategy. However, in sharply rising markets, the Fund is expected to underperform the same portfolio that does not employ a covered call option writing strategy. This underperformance in a sharply rising market could be significant. The Fund&#8217;s covered call option writing strategy may not fully protect it against declines in the value of the equity markets. The successful use of an option writing strategy depends in part on the ability of the portfolio managers to anticipate price fluctuations and the degree of correlation between the options and securities markets. Market volatility may also have a significant impact on the efficient execution and pricing of the option writing strategy. There are significant differences between the securities and options markets, which could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives.</p><p><b><i>Borrowing Risk.</i></b> Because the Fund may borrow money from banks for investment purposes, commonly referred to as &#8220;leveraging,&#8221; the Fund&#8217;s exposure to fluctuations in the prices of these securities is increased in relation to the Fund&#8217;s capital. The Fund&#8217;s borrowing activities will exaggerate any increase or decrease in the net asset value of the Fund. In addition, the interest which the Fund must pay on borrowed money, together with any additional fees to maintain a line of credit or any minimum average balances, are additional costs which will reduce or eliminate any net investment profits. Unless profits on assets acquired with borrowed funds exceed the costs of borrowing, the use of borrowing will diminish the investment performance of the Fund compared with what it would have been without borrowing.</p><p><b><i>Leverage Risk.</i></b> Leverage occurs when the Fund increases its assets available for investment through borrowings or similar transactions.</p><p><b><i>Nondiversification Risk.</i></b> The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund&#8217;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&#8217;s net asset value and total return.</p><p><b><i>Value Investing Risk.</i></b> Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, "value" stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected.</p><p><b><i>Derivatives Risk.</i></b> 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&#8217;s original cost, and can therefore involve leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations to the Fund.</p><p><i>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.</i></p>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringNarrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph i -Clause instruction -Subsection b falsefalseRisk Narrative [Text Block]28false0rr_RiskLoseMoneyrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The biggest risk is that the Fund&#8217;s returns will vary, and you could lose money.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringSummarize the principal risks of investing in the Fund, including the risks to which the Fund's portfolio as a whole is subject and the circumstances reasonably likely to affect adversely the Fund's net asset value, yield, and total return. Unless the Fund is a Money Market Fund, disclose that loss of money is a risk of investing in the Fund. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph i -Subsection b falsefalseRisk Lose Money [Text]29false0rr_RiskNondiversifiedStatusrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<b><i>Nondiversification Risk.</i></b>The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund&#8217;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&#8217;s net asset value and total return.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringIf applicable, state that the Fund is non-diversified, describe the effect of non-diversification (e.g., disclose that, compared with other funds, the Fund may invest a greater percentage of its assets in a particular issuer), and summarize the risks of investing in a non-diversified fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph iv -Subsection b falsefalseRisk Nondiversified Status [Text]30false0rr_RiskNotInsuredDepositoryInstitutionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<i>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.</i>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringIf the Fund is advised by or sold through an insured depository institution, state that An investment in the Fund is not a deposit of the bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. A Money Market Fund that is advised by or sold through an insured depository institution should combine the disclosure required by Items 2(c)(1)(ii) and (iii) in a single statement.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph iii -Subsection b falsefalseRisk Not Insured Depository Institution [Text]31false0rr_BarChartAndPerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00PERFORMANCE INFORMATIONfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart and Performance Table [Heading]32false0rr_PerformanceNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<p>The following information provides some indication of the risks of investing in the Fund by showing how the Fund&#8217;s performance has varied over time. Class&#160;I Shares, Class&#160;A Shares, Class&#160;C Shares, Class&#160;S Shares, and Class&#160;R Shares of the Fund commenced operations on July&#160;6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Long/Short Fund (&#8220;JAD predecessor fund&#8221;) into each respective share class of the Fund. Class&#160;T Shares of the Fund commenced operations on July&#160;6, 2009.</p><p>&#8226; The performance shown for Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund&#8217;s Class I Shares, Class A Shares, Class C Shares, Class S Shares, and Class R Shares prior to the reorganization, calculated using the fees and expenses of each respective share class of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.</p><p>&#8226; The performance shown for Class T Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund&#8217;s Class I Shares prior to the reorganization, calculated using the fees and expenses of Class I Shares, without the effect of any fee and expense limitations or waivers.</p><p>If Class T Shares of the Fund had been available during periods prior to July 6, 2009, the performance shown may have been different. The performance shown for periods following the Fund&#8217;s commencement of Class I Shares, Class A Shares, Class C Shares, Class S Shares, Class R Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.</p><p>The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund&#8217;s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund&#8217;s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.</p><p><i>The Fund&#8217;s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.</i></p>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalsePerformance Narrative [Text Block]33false0rr_PerformanceInformationIllustratesVariabilityOfReturnsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The following information provides some indication of the risks of investing in the Fund by showing how the Fund&#8217;s performance has varied over time. The bar chart depicts the change in performance from year to year during the periods indicated.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInclude the bar chart and table required by paragraphs (b)(2)(ii) and (iii) of this section. Provide a brief explanation of how the information illustrates the variability of the Fund's returns (e.g., by stating that the information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance). Provide a statement to the effect that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalsePerformance Information Illustrates Variability of Returns [Text]34false0rr_PerformanceAdditionalMarketIndexrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The table compares the Fund&#8217;s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInclude the bar chart and table required by paragraphs (b)(2)(ii) and (iii) of this section. Provide a brief explanation of how the information illustrates the variability of the Fund's returns (e.g., by stating that the information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance). Provide a statement to the effect that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalsePerformance Additional Market Index [Text]35false0rr_BarChartDoesNotReflectSalesLoadsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class&#160;A Shares or Class&#160;C Shares of the Fund. If sales charges were included, the returns would be lower.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInclude the bar chart and table required by Item 4 (b)(2)(ii) and (iii) of this section. Provide a brief explanation of how the information illustrates the variability of the Fund's returns (e.g., by stating that the information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance). Provide a statement to the effect that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Provide annual total returns beginning with the earliest calendar year. Calculate annual returns using the Instructions to Item 8(a), except that the calculations should be based on calendar years. If a Fund's shares are sold subject to a sales load or account fees, state that sales loads or account fees are not reflected in the bar chart and that, if these amounts were reflected, returns would be less than those shown.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalseBar Chart Does Not Reflect Sales Loads [Text]36false0rr_PerformancePastDoesNotIndicateFuturerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<i>The Fund&#8217;s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.</i>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInclude the bar chart and table required by paragraphs (b)(2)(ii) and (iii) of this section. Provide a brief explanation of how the information illustrates the variability of the Fund's returns (e.g., by stating that the information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance). Provide a statement to the effect that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalsePerformance Past Does Not Indicate Future [Text]37false0rr_PerformanceTableClosingTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<i>Updated performance information is available at janus.com/advisor/mutual-funds or by calling 1-877-335-2687.</i>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also shouldshow the returns of an appropriate broadbased securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Subsection b falsefalsePerformance Table Closing [Text Block]38false0rr_PerformanceAvailabilityWebSiteAddressrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<i>janus.com/advisor/mutual-funds</i>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringIf applicable, include a statement explaining that updated performance information is available and providing a Website address and/or toll-free (or collect) telephone number where the updated information may be obtained.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalsePerformance Availability Website Address [Text]39false0rr_PerformanceAvailabilityPhonerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<i>1-877-335-2687</i>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringIf applicable, include a statement explaining that updated performance information is available and providing a Web site address and/or toll-free (or collect) telephone number where the updated information may be obtained.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalsePerformance Availability Phone [Text]40false0rr_BarChartHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Annual Total Returns for Class I Shares (calendar year-end)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart [Heading]41false0rr_BarChartTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 <div> &lt;div style="display:none;"&gt;~ http://janus.com/role/AnnualTotalReturnsBarChartJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000010477_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsefalseBarChart36.jpg <div> &lt;div style="display:none;"&gt;~ http://janus.com/role/AnnualTotalReturnsBarChartJanusLongShortFund column period compact * column rr_ProspectusShareClassAxis compact * row primary compact * row dei_DocumentInformationDocumentAxis compact jif277751_S000010477_Member * row dei_LegalEntityAxis compact jif277751_Prospectus_Eight_Member * ~&lt;/div&gt; </div>falsehttp://janus.com/role/AnnualTotalReturnsBarChartJanusLongShortFundfalsefalse0200535 - Schedule - Annual Total Returns (Bar Chart) - Janus Long/Short Fund (Class A, C, S, I & T Shares)truefalsefalse1falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseJanus Long/Short Fund [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_S000025891Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseClass I, Janus Long/Short Fund [Member]rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_C000077611Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberJanus Long/Short Fund [Member]Class I, Janus Long/Short Fund [Member]Alternative - Class A, C, S, I, R and T Shares [Member]USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*4false0rr_AnnualReturn2007rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.16560.1656falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalse20070rr_AnnualReturn2007truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.16560.1656falsefalsefalsetruefalseOthernanafalsefalse20072falseRowprimaryElement*5false0rr_AnnualReturn2008rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse-0.2368-0.2368falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalse20080rr_AnnualReturn2008truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.2368-0.2368falsefalsefalsetruefalseOthernanafalsefalse20083falseRowprimaryElement*6false0rr_AnnualReturn2009rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.04560.0456falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalse20090rr_AnnualReturn2009truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.04560.0456falsefalsefalsetruefalseOthernanafalsefalse20094falseRowprimaryElement*7false0rr_AnnualReturn2010rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruefalse0.02780.0278falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalse20100rr_AnnualReturn2010truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.02780.0278falsefalsefalsetruefalseOthernanafalsefalse201014Annual Total Returns (Bar Chart) - Janus Long/Short Fund (Class A, C, S, I & T Shares) UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxis*Columnrr_ProspectusShareClassAxisAxis*Columndei_LegalEntityAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to BarChartData.No authoritative reference available.falsefalseBar Chart [Table]42false0rr_BarChartClosingTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Best Quarter: Third Quarter 2009 9.28% Worst Quarter: First Quarter 2009 -13.38%falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseBar Chart Closing [Text Block]43false0rr_AverageAnnualReturnCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Average Annual Total Returns (periods ended 12/31/10)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. 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If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalseLabelfalseUSDfalsefalse$3falseColumnprimaryElement*6false0rr_IndexNoDeductionForFeesExpensesTaxesrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalse8falsefalsefalse00falsefalsefalsetruefalse9falsefalsefalse00(reflects no deduction for expenses, fees, or taxes)falsefalsefalsetruefalse10falsefalsefalse00(reflects no deduction for expenses, fees, or taxes)falsefalsefalsetruefalseOtherxbrli:stringItemTypestringThe Performance Table includes a parenthetical, indicating that the Index "(reflects no deduction for fees, expenses or taxes)". 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Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberS&P 500 Index [Member]Inception Period Since, 08-01-2006 [Member]Share ClassesAlternative - Class A, C, S, I, R and T Shares [Member]Standard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsetruefalse00S&P 500&#174; IndexS&P 500&#174; Indexfalsefalsefalsetruefalse3falsefalsefalse00(reflects no deduction for expenses, fees, or taxes)(reflects no deduction for expenses, fees, or taxes)falsefalsefalsetruefalse4truetruetrue0.15060.1506falsefalsefalsetruefalse5truetruetrue0.01940.0194falsefalsefalsetruefalse6falsetruefalse002006-08-012006-08-01falsefalsetruetruefalseOthernanafalsefalseS&P 500 Index [Member] Inception Period Since, 08-01-2006 [Member]10falseRowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*duration2010-01-29T00:00:002011-01-28T00:00:00falsefalseLIBOR [Member]dei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_LiborMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseInception Period Since, 08-01-2006 [Member]rr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_InceptionPeriodSixteenMemberrr_PerformanceMeasureAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberfalsefalseAlternative - Class A, C, S, I, R and T Shares [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldijif277751_ProspectusEightMemberdei_LegalEntityAxisexplicitMemberLIBOR [Member]Inception Period Since, 08-01-2006 [Member]Share ClassesAlternative - Class A, C, S, I, R and T Shares [Member]Standard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsetruefalse00LIBORLIBORfalsefalsefalsetruefalse3falsefalsefalse00(reflects no deduction for expenses, fees, or taxes)(reflects no deduction for expenses, fees, or taxes)falsefalsefalsetruefalse4truetruetrue0.00340.0034falsefalsefalsetruefalse5truetruetrue0.02530.0253falsefalsefalsetruefalse6falsetruefalse002006-08-012006-08-01falsefalsetruetruefalseOthernanafalsefalseLIBOR [Member] Inception Period Since, 08-01-2006 [Member]1Calculated assuming maximum permitted sales loads.2The one year return is calculated to include the contingent deferred sales charge.3If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund's other return figures. 610Average Annual Total Returns - Janus Long/Short Fund (Class A, C, S, I & T Shares) Alternative - Class A, C, S, I, R and T Shares [Member]UnKnownUnKnownUnKnownUnKnownfalsetrueColumnprimaryElement*RowperiodPeriod*Rowdei_DocumentInformationDocumentAxisAxis*Rowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowdei_LegalEntityAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to PerformanceTableData.No authoritative reference available.falsefalsePerformance [Table]45false0rr_PerformanceTableNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<p>After-tax returns are calculated using distributions for the Fund&#8217;s Class&#160;I Shares for periods following July&#160;6, 2009; and for the JAD predecessor fund&#8217;s Class&#160;I Shares for periods prior to July&#160;6, 2009. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.</p><p>After-tax returns are only shown for Class&#160;I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class&#160;I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.</p>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also shouldshow the returns of an appropriate broadbased securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____). For a Fund that provides annual total returns for only one calendar year or for a Fund that does not include the bar chart because it does not have annual returns for a full calendar year, modify, as appropriate, the narrative explanation required by paragraph (c)(2)(i) (e.g., by stating that the information gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Subsection b falsefalsePerformance Table Narrative46false0rr_PerformanceTableUsesHighestFederalRaterrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringProvide a brief explanation that after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Subsection b falsefalsePerformance Table Uses Highest Federal Rate47false0rr_PerformanceTableNotRelevantToTaxDeferredrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-deferred account, such as a 401(k) plan or an IRA.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringProvide a brief explanation that the actual after-tax returns depend on an investor's tax situation and may differ from those shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Clause B -Subsection b falsefalsePerformance Table Not Relevant to Tax Deferred48false0rr_PerformanceTableOneClassOfAfterTaxShownrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00After-tax returns are only shown for Class&#160;I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class&#160;I Shares due to varying sales charges (as applicable), fees, and expenses among the classes.falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringProvide a brief explanation that if the Fund is a Multiple Class Fund that offers more than one Class in the prospectus, after-tax returns are shown for only one Class and after-tax returns for other Classes will vary.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Subsection b Reference 2: 2 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Clause C -Subsection b falsefalsePerformance Table One Class of after Tax Shown [Text]147Risk/Return Summary - Janus Long/Short Fund (Class A, C, S, I, R & T Shares) (Janus Long/Short Fund [Member], Alternative - Class A, C, S, I, R and T Shares [Member], USD $)NoRoundingUnKnownUnKnownUnKnowntruetrue