Janus Henderson Overseas Portfolio Performance Management - Institutional Shares [Member] - Janus Henderson Overseas Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Performance information</span>
Performance Narrative [Text Block]	The following information provides some indication of the risks of investing in the Portfolio by showing how the Portfolio’s performance has varied over time. The bar chart depicts the change in performance from year to year during the periods indicated. Total return figures include the effect of the Portfolio’s expenses, but do not include charges or expenses attributable to any insurance product, which would lower the performance illustrated.The table compares the average annual returns for the Institutional Shares of the Portfolio for the periods indicated to a broad-based securities market index. All figures assume reinvestment of dividends and distributions.The Portfolio’s past performance does not necessarily indicate how it will perform in the future.Updated performance information is available at janushenderson.com/VITperformance or by calling 1-877-335-2687.
Performance Past Does Not Indicate Future [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">The Portfolio’s past performance does not necessarily indicate how it will perform in the future.</span>
Performance Information Illustrates Variability of Returns [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The following information provides some indication of the risks of investing in the Portfolio by showing how the Portfolio’s performance has varied over time. The bar chart depicts the change in performance from year to year during the periods indicated. Total return figures include the effect of the Portfolio’s expenses, but do not include charges or expenses attributable to any insurance product, which would lower the performance illustrated.</span>
Performance Additional Market Index [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The table compares the average annual returns for the Institutional Shares of the Portfolio for the periods indicated to a broad-based securities market index. All figures assume reinvestment of dividends and distributions.</span>
Bar Chart [Heading]	Annual Total Returns for Institutional Shares (calendar year-end)
Bar Chart Closing [Text Block]	Best Quarter:4th Quarter 202021.18%Worst Quarter:1st Quarter 2020– 24.90%
Performance Table Heading	Average Annual Total Returns (periods ended 12/31/25)
Performance Table Narrative	The Portfolio’s broad-based benchmark index is the MSCI All Country World ex-USA Index. The index is described below. •The MSCI All Country World ex-USA Index is designed to measure equity market performance in global developed and emerging markets outside the United States.
Performance Table Closing [Text Block]	Updated performance information is available at janushenderson.com/VITperformance or by calling 1-877-335-2687.
Performance Availability Website Address [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">janushenderson.com/</span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">VITperformance</span>
Performance Availability Phone [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">1-877-335-2687</span>
Institutional Shares
Prospectus [Line Items]
Highest Quarterly Return, Label [Optional Text]	Best Quarter
Highest Quarterly Return	21.18%
Highest Quarterly Return, Date	Dec. 31, 2020
Lowest Quarterly Return, Label [Optional Text]	Worst Quarter
Lowest Quarterly Return	(24.90%)
Lowest Quarterly Return, Date	Mar. 31, 2020