Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS ASPEN SERIES
Prospectus Date	rr_ProspectusDate	Sep. 06, 2012
Janus Aspen INTECH U.S. Low Volatility Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Portfolio summary Janus Aspen INTECH U.S. Low Volatility Portfolio
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	INTECH U.S. Low Volatility Portfolio seeks capital appreciation.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Shares of the Portfolio. Owners of variable insurance contracts that invest in the Shares should refer to the variable insurance contract prospectus for a description of fees and expenses, as the following table and examples do not reflect deductions at the separate account level or contract level for any charges that may be incurred under a contract. Inclusion of these charges would increase the fees and expenses described below.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Portfolio’s performance.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Since the Portfolio is new, Other Expenses are based on the estimated expenses that the Portfolio expects to incur in its initial fiscal period.
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE:
Expense Example by Year [Heading]	rr_ExpenseExampleByYearHeading	The Example assumes that you invest $10,000 in the Portfolio for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Portfolio’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The Example is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds.
Strategy [Heading]	rr_StrategyHeading	PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Portfolio invests, under normal circumstances, at least 80% of its net assets in U.S. stocks from the universe of the S&P 500® Index utilizing INTECH’s mathematical investment process. The S&P 500® Index is an unmanaged index of 500 stocks that is generally representative of the performance of larger companies in the United States. The Portfolio seeks to achieve market-like returns over the long-term, with lower absolute volatility than the S&P 500® Index (the Portfolio’s benchmark index). In this context, absolute volatility refers to the variation in the returns of the Portfolio. Over time, and under normal market conditions, the Portfolio seeks to generate returns equal to those of the S&P 500® Index but with absolute volatility approximately 20%-40% lower than the S&P 500® Index. The Portfolio pursues its investment objective by applying a mathematical investment process to construct an investment portfolio from the universe of stocks within the S&P 500® Index. The goal of this process is to combine stocks that individually have higher relative volatility and lower correlations with each other in an effort to reduce the Portfolio’s absolute volatility, while still generating market-like returns over a full market cycle. Although the Portfolio may underperform its benchmark in sustained up markets, this strategy seeks to minimize losses in down markets. In applying this strategy, INTECH establishes target proportions of its holdings from stocks within the S&P 500® Index using an optimization process designed to determine the most effective weightings of each stock in the Portfolio. Once INTECH determines such proportions and the Portfolio’s investments are selected, the Portfolio is periodically rebalanced to the set target proportions and re-optimized. The rebalancing techniques used by INTECH may result in a higher portfolio turnover compared to a “buy and hold” strategy.
Risk [Heading]	rr_RiskHeading	PRINCIPAL INVESTMENT RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The biggest risk is that the Portfolio’s returns will vary, and you could lose money. The Portfolio is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices. Market Risk. The value of the Portfolio’s holdings may decrease if the value of an individual company or security, or multiple companies or securities, in the Portfolio decreases. Further, regardless of how well individual companies or securities perform, the value of the Portfolio’s holdings could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money. Investment Process Risk. The proprietary mathematical investment process used by INTECH may not achieve the desired results. On an occasional basis, INTECH considers changes to its mathematical investment process. These changes may result in changes to the Portfolio, might not provide the intended results, and may adversely impact the Portfolio’s performance. In particular, INTECH’s low volatility strategy may underperform the S&P 500® Index during certain periods of up markets and may not achieve the desired level of protection in down markets. Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Portfolio’s performance. An investment in the Portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	The biggest risk is that the Portfolio’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the Portfolio is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	PERFORMANCE INFORMATION
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Portfolio does not have a full calendar year of operations. Performance information for certain periods will be included in the Portfolio’s first annual and/or semiannual report.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Portfolio does not have a full calendar year of operations.
Janus Aspen INTECH U.S. Low Volatility Portfolio | Service Shares
Risk/Return:	rr_RiskReturnAbstract
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	Service Shares
Management Fees	rr_ManagementFeesOverAssets	0.50%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.16%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.91%
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Service Shares
1 Year	rr_ExpenseExampleYear01	92
3 Years	rr_ExpenseExampleYear03	289

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