Janus Henderson Mid Cap Value Portfolio Investment Strategy - Service Shares [Member] - Janus Henderson Mid Cap Value 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 primarily in the common stocks of mid-sized companies and focuses on companies whose stock prices are believed to be undervalued by portfolio management or that have fallen out of favor with the market. The Portfolio invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of companies whose market capitalization falls, at the time of purchase, within the 12-month capitalization range of the Russell Midcap® Value Index. The market capitalizations within the index will vary, but as of December 31, 2025, they ranged from approximately $122 million to $83.54 billion. From time to time, the Portfolio may invest in shares of companies through initial public offerings. The Portfolio may also invest in foreign securities, as well as in real estate investment trusts (“REITs”) and similar REIT-like entities. As defensive value managers, portfolio management generally looks for companies with: •strong management teams; •strong and stable balance sheets and solid recurring free cash flows; •attractive relative and absolute valuation ratios or that have underperformed recently; •favorable reward to risk characteristics; •sustainable competitive advantages that are trading at attractive valuations; and •strong long-term prospects. Portfolio management’s philosophy is to weigh a security’s downside risk before considering its upside potential, which may help provide an element of capital preservation.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.

Janus Henderson Mid Cap Value Portfolio Investment Strategy - Service Shares [Member] - Janus Henderson Mid Cap Value 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 primarily in the common stocks of mid-sized companies and focuses on companies whose stock prices are believed to be undervalued by portfolio management or that have fallen out of favor with the market. The Portfolio invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of companies whose market capitalization falls, at the time of purchase, within the 12-month capitalization range of the Russell Midcap® Value Index. The market capitalizations within the index will vary, but as of December 31, 2025, they ranged from approximately $122 million to $83.54 billion. From time to time, the Portfolio may invest in shares of companies through initial public offerings. The Portfolio may also invest in foreign securities, as well as in real estate investment trusts (“REITs”) and similar REIT-like entities. As defensive value managers, portfolio management generally looks for companies with: •strong management teams; •strong and stable balance sheets and solid recurring free cash flows; •attractive relative and absolute valuation ratios or that have underperformed recently; •favorable reward to risk characteristics; •sustainable competitive advantages that are trading at attractive valuations; and •strong long-term prospects. Portfolio management’s philosophy is to weigh a security’s downside risk before considering its upside potential, which may help provide an element of capital preservation.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.