Janus Henderson Forty Portfolio Investment Risks - Service Shares [Member] - Janus Henderson Forty Portfolio	Dec. 31, 2025
Market Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Market Risk. The value of the Portfolio’s holdings may decrease due to short-term market movements and over more prolonged market downturns. As a result, the Portfolio’s net asset value may fluctuate and it may be more difficult to value or sell the Portfolio’s holdings. Market risk may affect a single issuer, industry, economic sector, or the market as a whole. Market risk may be magnified if certain social, political, economic, and other conditions and events (such as financial institution failures, economic recessions, tariffs, trade disputes, terrorism, war, armed conflicts, including related sanctions, social unrest, natural disasters, and epidemics and pandemics) adversely interrupt the global economy and financial markets. 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.
Portfolio Management Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Portfolio Management Risk. The Portfolio is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies and research process employed for the Portfolio may fail to produce the intended results. Accordingly, the Portfolio may underperform benchmark indices or other funds with similar investment objectives.
Growth Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Growth Securities Risk. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If portfolio management’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Portfolio’s returns. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from other types of securities and the market as a whole.
Large Sized Companies Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Large-Sized Companies Risk. Large-sized companies may be less able than smaller-sized companies to adapt to changing market conditions. Large-sized companies may be more mature and subject to more limited growth potential compared with smaller sized companies. During different market cycles, the performance of large-sized companies has trailed the overall performance of the broader securities markets.
Equity Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Equity Securities Risk. Equity securities are subject to changes in value, and their values may be more volatile than those of other asset classes. 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 or perceptions regarding the industries in which the issuers of securities the Portfolio holds participate.
Issuer Concentration Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Issuer Concentration Risk. The Portfolio’s holdings may be comprised of a relatively small number of issuers in comparison to other portfolios. As a result, the Portfolio may be subject to greater risks than a portfolio that invests in a greater number of issuers. A change in the value of any single investment held by the Portfolio may affect the overall value of the Portfolio more than it would affect a portfolio that holds more investments. In particular, the Portfolio may be more susceptible to adverse developments affecting any single issuer held by the Portfolio and may be susceptible to greater losses because of these developments. The Portfolio’s policy of concentrating its portfolio in a smaller number of holdings could result in more volatility in the Portfolio’s performance and share price.
Industry and Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Industry and Sector Risk. Although the Portfolio does not concentrate its investments in specific industries, it may have a significant portion of its assets invested in securities of companies conducting similar business or businesses within the same economic sector. Companies in the same industry or economic sector may be similarly affected by negative economic or market events, making the Portfolio more vulnerable to unfavorable developments than portfolios that invest more broadly. As the Portfolio’s holdings become more concentrated, the Portfolio is less able to spread risk and potentially reduce the risk of loss and volatility. As the Portfolio’s holdings change over time, the Portfolio’s exposure to a particular economic sector may fluctuate.
Technology Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	•Technology Sector Risk. In the technology sector, competitive pressures may have a significant effect on the performance of companies in which the Portfolio may invest. In addition, technology and technology-related companies often progress at an accelerated rate, and these companies may be subject to short product cycles and aggressive pricing, which may increase their volatility.
Foreign Exposure Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Foreign Exposure Risk. Foreign markets can be more volatile than the U.S. market. As a result, the Portfolio’s returns and net asset value may be affected by fluctuations in currency exchange rates or political or economic conditions in a particular country. Investments in foreign securities, particularly those of issuers located in emerging market countries, tend to have greater exposure to liquidity risk than domestic securities. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Portfolio to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Portfolio has invested a significant amount of its assets may have a greater effect on the Portfolio’s performance than it would in a more geographically diversified portfolio.
Mid-Sized Companies Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Mid-Sized Companies Risk. Investments in securities issued by mid-sized companies may involve greater risks than are customarily associated with larger, more established companies. Securities issued by mid-sized companies tend to be more volatile than securities issued by larger or more established companies and may underperform as compared to the securities of larger or more established companies. These holdings are also subject to wider price fluctuations and tend to be less liquid than stocks of larger or more established companies, which could have a significant adverse effect on the Portfolio’s returns, especially as market conditions change.
Securities Lending Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Securities Lending Risk. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Portfolio may experience delays and costs in recovering the security or gaining access to the collateral provided to the Portfolio to collateralize the loan. If the Portfolio is unable to recover a security on loan, the Portfolio may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Portfolio.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	The biggest risk is that the Portfolio’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Member]
Prospectus [Line Items]
Risk [Text Block]	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 Nondiversified Status [Member]
Prospectus [Line Items]
Risk [Text Block]	Nondiversification Risk. The Portfolio is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives portfolio management more flexibility to hold larger positions in more securities than a portfolio that is classified as diversified. As a result, an increase or decrease in the value of a single security held by the Portfolio may have a greater impact on the Portfolio’s net asset value and total return.