Prospectus: Risk/Return: Document Type Document Period End Date Registrant Name Central Index Key Amendment Flag Amendment Description Trading Symbol Document Creation Date Document Effective Date Prospectus Date Series [Axis] Series Janus Conservative Allocation Fund Member S000010483 [Member] Janus Conservative Allocation Fund Document [Axis] Prospectus Class Acsit Shares. Class Acsit Shares [Member] Class A, C, S, I, T Shares Performance Measure [Axis] Before Taxes Return Before Taxes Return After Taxes on Distributions and Sale of Fund Shares After Taxes on Distributions and Sales After Taxes on Distributions Return After Taxes on Distributions Share Class [Axis] Share Classes Class A,Janus Conservative Allocation Fund Member Class A Class A Shares C000077718 [Member] Class C Shares C000077719 [Member] Class C Class C,Janus Conservative Allocation Fund Member Class I,Janus Conservative Allocation Fund Member C000077720 [Member] Class I Shares Class I Class S Class S,Janus Conservative Allocation Fund Member C000077721 [Member] Class S Shares Class T Class T,Janus Conservative Allocation Fund Member Class T Shares C000028943 [Member] Risk/Return [Heading] Objective [Heading] Objective, Primary [Text Block] Objective, Secondary [Text Block] Expense [Heading] Expense Narrative [Text Block] Expense Breakpoint Discounts [Text] Shareholder Fees Caption [Text] Shareholder Fees [Table] Operating Expenses Caption [Text] Annual Fund Operating Expenses [Table] Expense Footnotes [Text Block] Expenses Deferred Charges [Text Block] Expenses Range of Exchange Fees [Text Block] Expense Example [Heading] Expense Example Narrative [Text Block] Expense Example by Year [Heading] Expense Example by, Year, Caption [Text] Expense Example, With Redemption [Table] Expense Example, No Redemption Narrative [Text Block] Expense Example, No Redemption, By Year, Caption [Text] Expense Example, No Redemption [Table] Expense Example Footnotes [Text Block] Expense Example Closing [Text Block] Portfolio Turnover [Heading] Portfolio Turnover [Text Block] Strategy [Heading] Strategy Narrative [Text Block] Risk [Heading] Risk Narrative [Text Block] Risk Footnotes [Text Block] Risk Closing [Text Block] Bar Chart and Performance Table [Heading] Performance Narrative [Text Block] Bar Chart Narrative [Text Block] Bar Chart [Heading] Bar Chart [Table] Bar Chart Footnotes [Text Block] Bar Chart Closing [Text Block] Year to Date Return, Label Performance Table Heading Performance [Table] Performance Table Narrative Market Index Performance [Table] Performance Table Footnotes Shareholder Fees: Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds) Maximum Deferred Sales Charge (as a percentage) Shareholder Fees Column [Text] Maximum Cumulative Sales Charge (as a percentage of Offering Price) Maximum Cumulative Sales Charge (as a percentage) Maximum Deferred Sales Charge (as a percentage of Offering Price) Maximum Sales Charge on Reinvested Dividends and Distributions (as a percentage) Redemption Fee (as a percentage of Amount Redeemed) Redemption Fee (as a percentage of Amount Redeemed) Redemption Fee Redemption Fee Exchange Fee (as a percentage of Amount Redeemed) Exchange Fee Maximum Account Fee (as a percentage of Assets) Maximum Account Fee Shareholder Fee, Other Operating Expenses: Management Fees Management Fees (as a percentage of Assets) Management Fees (may adjust up or down) Distribution/Service (12b-1) Fees Distribution and Service (12b-1) Fees Other Expenses Other Expenses (as a percentage of Assets): Acquired Fund Fees and Expenses Acquired Fund Fees and Expenses Total Annual Fund Operating Expenses Expenses (as a percentage of Assets) Total Annual Fund Operating Expenses Net Expenses (as a percentage of Assets) Total Annual Fund Operating Expenses After Fee Waiver Total Annual Fund Operating Expenses After Fee Waiver Operating Expenses Column [Text] Distribution or Similar (Non 12b-1) Fees Component1 Other Expenses Component2 Other Expenses Component3 Other Expenses Fee Waiver Fee Waiver or Reimbursement Fee Waiver Expense Example: 1 Year Expense Example, with Redemption, 1 Year 1 Year 3 Years Expense Example, with Redemption, 3 Years 3 Years 5 Years Expense Example, with Redemption, 5 Years 5 Years 10 Years Expense Example, with Redemption, 10 Years 10 Years Expense Example, By Year, Column [Text] Column Expense Example, No Redemption: 1 Year Expense Example, No Redemption, 1 Year 1 Year 3 Years Expense Example, No Redemption, 3 Years 5 Years Expense Example, No Redemption, 5 Years 10 Years Expense Example, No Redemption, 10 Years Column Expense Example, No Redemption, By Year, Column [Text] Bar Chart Table: Caption Annual Return Caption [Text] Column Annual Return, Column [Text] Annual Return, Inception Date Inception Date Annual Return 1990 Annual Return 1991 Annual Return 1992 Annual Return 1993 Annual Return 1994 Annual Return 1995 Annual Return 1996 Annual Return 1997 Annual Return 1998 Annual Return 1999 Annual Return 2000 Annual Return 2001 Annual Return 2002 2002 2003 Annual Return 2003 2004 Annual Return 2004 Annual Return 2005 2005 2006 Annual Return 2006 Annual Return 2007 2007 2008 Annual Return 2008 2009 Annual Return 2009 Annual Return 2010 2010 2011 Annual Return 2011 Annual Return 2012 Annual Return 2013 Annual Return 2014 Annual Return 2015 Annual Return 2016 Annual Return 2017 Annual Return 2018 Annual Return 2019 Annual Return 2020 Return Before Taxes Return Before Taxes. Return Before Taxes [Member] S&P 500 Index (reflects no deduction for expenses, fees, or taxes). S And P Five Hundred Index [Member] S&P 500 Index (reflects no deduction for expenses, fees, or taxes) Conservative Allocation Index [Member] Conservative Allocation Index (reflects no deduction for expenses, fees, or taxes). Conservative Allocation Index (reflects no deduction for expenses, fees, or taxes) Average Annual Return: 1 Year 1 Year 5 Years 5 Years Since Inception Since Inception Since Inception of Predecessor Fund Inception Date Inception Date Column Label 10 Years 10 Years