Janus Henderson Overseas Portfolio Investment Strategy - Service Shares [Member] - Janus Henderson Overseas Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Principal investment strategies</span>
Strategy Narrative [Text Block]	The Portfolio pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in securities of issuers or companies from countries outside of the United States. The Portfolio normally invests in a portfolio of 30-50 securities of issuers from several different countries, excluding the United States, and it may, under unusual circumstances, invest all or substantially all of its assets in a single country. The Portfolio may invest up to 20% of its net assets, measured at the time of purchase, in U.S. issuers. An issuer is deemed to be from a country or countries outside of the United States if one or more of the following tests are met: (i) the issuer is organized in, or its primary business office or principal trading market of its equity is located in, a country outside of the United States; (ii) a majority of the issuer’s revenues are derived from outside of the United States; or (iii) a majority of the issuer’s assets are located outside of the United States. The Portfolio may have significant exposure to emerging markets. The Portfolio typically invests in equity securities (such as stocks or any other security representing an ownership interest) in all market capitalizations. Portfolio management applies a “bottom-up” approach in choosing investments. In other words, portfolio management looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Portfolio’s investment policies. Portfolio management will generally consider selling a security when, among other things, the security no longer reflects portfolio management’s investment thesis, the security approaches or exceeds its targeted value, there has been a change in a security’s risk/reward potential, or a better idea is identified.The Portfolio may take long or short positions in derivatives. Derivatives are instruments that have a value derived from, or directly linked to, an underlying asset, such as equity securities, commodities, currencies, interest rates, or market indices. For purposes of meeting its 80% investment policy, the Portfolio may include derivatives that have characteristics similar to the securities in which the Portfolio may directly invest. The types of derivatives in which the Portfolio may invest include options, futures, swaps, warrants, and forward foreign currency contracts. The Portfolio may use derivatives to hedge, to earn income or enhance returns, as a substitute for securities in which the Portfolio invests, to increase or decrease the Portfolio’s exposure to a particular market, to adjust the Portfolio’s currency exposure relative to its benchmark index, to gain access to foreign markets where direct investment may be restricted or unavailable, or to manage the Portfolio’s risk profile.As part of its investment process, portfolio management considers environmental, social, and governance (“ESG”) risks and opportunities (“ESG Factors”) that it believes are financially material, alongside other fundamental investment factors. Examples of potential financially material ESG Factors include: corporate governance, company culture, exposure to climate change, and human capital management. To assess ESG Factors, portfolio management uses issuer reports, third-party data, and internally-generated analyses and may engage directly with issuers. ESG Factors are one of many considerations in the investment decision-making process, may not be determinative in deciding to include or exclude an investment from the portfolio, and may not be considered for every investment decision.The Portfolio may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.

Janus Henderson Overseas Portfolio Investment Strategy - Service Shares [Member] - Janus Henderson Overseas Portfolio

Dec. 31, 2025

<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Principal investment strategies</span>

Strategy Narrative [Text Block]

The Portfolio pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in securities of issuers or companies from countries outside of the United States. The Portfolio normally invests in a portfolio of 30-50 securities of issuers from several different countries, excluding the United States, and it may, under unusual circumstances, invest all or substantially all of its assets in a single country. The Portfolio may invest up to 20% of its net assets, measured at the time of purchase, in U.S. issuers. An issuer is deemed to be from a country or countries outside of the United States if one or more of the following tests are met: (i) the issuer is organized in, or its primary business office or principal trading market of its equity is located in, a country outside of the United States; (ii) a majority of the issuer’s revenues are derived from outside of the United States; or (iii) a majority of the issuer’s assets are located outside of the United States. The Portfolio may have significant exposure to emerging markets. The Portfolio typically invests in equity securities (such as stocks or any other security representing an ownership interest) in all market capitalizations. Portfolio management applies a “bottom-up” approach in choosing investments. In other words, portfolio management looks at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Portfolio’s investment policies. Portfolio management will generally consider selling a security when, among other things, the security no longer reflects portfolio management’s investment thesis, the security approaches or exceeds its targeted value, there has been a change in a security’s risk/reward potential, or a better idea is identified.The Portfolio may take long or short positions in derivatives. Derivatives are instruments that have a value derived from, or directly linked to, an underlying asset, such as equity securities, commodities, currencies, interest rates, or market indices. For purposes of meeting its 80% investment policy, the Portfolio may include derivatives that have characteristics similar to the securities in which the Portfolio may directly invest. The types of derivatives in which the Portfolio may invest include options, futures, swaps, warrants, and forward foreign currency contracts. The Portfolio may use derivatives to hedge, to earn income or enhance returns, as a substitute for securities in which the Portfolio invests, to increase or decrease the Portfolio’s exposure to a particular market, to adjust the Portfolio’s currency exposure relative to its benchmark index, to gain access to foreign markets where direct investment may be restricted or unavailable, or to manage the Portfolio’s risk profile.As part of its investment process, portfolio management considers environmental, social, and governance (“ESG”) risks and opportunities (“ESG Factors”) that it believes are financially material, alongside other fundamental investment factors. Examples of potential financially material ESG Factors include: corporate governance, company culture, exposure to climate change, and human capital management. To assess ESG Factors, portfolio management uses issuer reports, third-party data, and internally-generated analyses and may engage directly with issuers. ESG Factors are one of many considerations in the investment decision-making process, may not be determinative in deciding to include or exclude an investment from the portfolio, and may not be considered for every investment decision.The Portfolio may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.