Janus Henderson Flexible Bond Portfolio Investment Strategy - Institutional Shares [Member] - Janus Henderson Flexible Bond 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 primarily investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in bonds. Bonds include, but are not limited to, government notes and bonds, corporate bonds, commercial and residential mortgage-backed securities, asset-backed securities, credit risk transfer securities (“CRTs”), and money market instruments. The Portfolio may invest in fixed and floating rate obligations with varying durations. The Portfolio’s average portfolio duration typically ranges between three and seven years. As of December 31, 2025, the Portfolio’s average portfolio duration was 5.88 years. The Portfolio will invest at least 65% of its net assets in investment grade debt securities. The Portfolio will limit its investment in high-yield bonds (also known as “junk” bonds) to 35% or less of its net assets. The Portfolio generates total return from a combination of current income and capital appreciation, but income is usually the dominant portion. The Portfolio may enter into “to be announced” or “TBA” commitments when purchasing mortgage-backed securities or other securities. The Portfolio also invests in securities that have contractual restrictions that prohibit or limit their public resale, which may include Rule 144A securities. The Portfolio may also invest in foreign securities. Due to the nature of the securities in which the Portfolio invests, it may have relatively high portfolio turnover compared to other portfolios. Additionally, the Portfolio may invest its assets in derivatives. Derivative instruments have a value derived from, or directly linked to, an underlying asset, such as fixed-income securities, commodities, currencies, interest rates, or market indices. In particular, the Portfolio may use futures, including Treasury bond futures, to manage interest rate risk, yield curve positioning, and country exposure. The Portfolio may also use index credit default swaps for hedging purposes (to offset risks associated with an investment exposure, or market conditions), to increase or decrease the Portfolio’s exposure to a particular market, to manage or adjust the risk profile of the Portfolio relative to its benchmark index, and to earn income, enhance returns, or preserve capital. The Portfolio’s exposure to derivatives will vary. 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 Portfolio may take short positions on derivatives instruments. Portfolio management’s investment process is research-driven, incorporating “top-down” and “bottom-up” factors to identify and manage exposure to risks across sectors, industries, and individual investments. Portfolio management evaluates expected risk-adjusted returns on a portfolio and position level by analyzing fundamentals, valuations, and market technical indicators. This research encompasses both traditional fundamental analysis and data driven quantitative models and signals from such models.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 Flexible Bond Portfolio Investment Strategy - Institutional Shares [Member] - Janus Henderson Flexible Bond 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 primarily investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in bonds. Bonds include, but are not limited to, government notes and bonds, corporate bonds, commercial and residential mortgage-backed securities, asset-backed securities, credit risk transfer securities (“CRTs”), and money market instruments. The Portfolio may invest in fixed and floating rate obligations with varying durations. The Portfolio’s average portfolio duration typically ranges between three and seven years. As of December 31, 2025, the Portfolio’s average portfolio duration was 5.88 years. The Portfolio will invest at least 65% of its net assets in investment grade debt securities. The Portfolio will limit its investment in high-yield bonds (also known as “junk” bonds) to 35% or less of its net assets. The Portfolio generates total return from a combination of current income and capital appreciation, but income is usually the dominant portion. The Portfolio may enter into “to be announced” or “TBA” commitments when purchasing mortgage-backed securities or other securities. The Portfolio also invests in securities that have contractual restrictions that prohibit or limit their public resale, which may include Rule 144A securities. The Portfolio may also invest in foreign securities. Due to the nature of the securities in which the Portfolio invests, it may have relatively high portfolio turnover compared to other portfolios. Additionally, the Portfolio may invest its assets in derivatives. Derivative instruments have a value derived from, or directly linked to, an underlying asset, such as fixed-income securities, commodities, currencies, interest rates, or market indices. In particular, the Portfolio may use futures, including Treasury bond futures, to manage interest rate risk, yield curve positioning, and country exposure. The Portfolio may also use index credit default swaps for hedging purposes (to offset risks associated with an investment exposure, or market conditions), to increase or decrease the Portfolio’s exposure to a particular market, to manage or adjust the risk profile of the Portfolio relative to its benchmark index, and to earn income, enhance returns, or preserve capital. The Portfolio’s exposure to derivatives will vary. 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 Portfolio may take short positions on derivatives instruments. Portfolio management’s investment process is research-driven, incorporating “top-down” and “bottom-up” factors to identify and manage exposure to risks across sectors, industries, and individual investments. Portfolio management evaluates expected risk-adjusted returns on a portfolio and position level by analyzing fundamentals, valuations, and market technical indicators. This research encompasses both traditional fundamental analysis and data driven quantitative models and signals from such models.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.