Janus Henderson Research Portfolio Performance Management - Institutional Shares [Member] - Janus Henderson Research 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, as well as to one or more additional indices that have investment characteristics similar to those of the Portfolio. 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, as well </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">as to one or more additional indices that have investment characteristics similar to those of the Portfolio. 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:2nd Quarter 202026.72%Worst Quarter:2nd Quarter 2022– 22.28%
Performance Table Heading	Average Annual Total Returns (periods ended 12/31/25)
Performance Table Narrative	The Portfolio’s broad-based benchmark index is the Russell 1000 Index due to regulatory requirements. The Portfolio’s additional benchmark index is the Russell 1000 Growth Index, which has investment characteristics similar to those of the Portfolio. The Portfolio’s additional benchmark is the S&P 500 Index. The indices are described below. •The Russell 1000 Index measures the performance of the large-cap segment of the U.S. equity universe. •The Russell 1000 Growth Index measures the performance of those Russell 1000 companies with higher price-to-book ratios and higher forecasted growth values. •The S&P 500 Index is a commonly recognized, market capitalization-weighted index of 500 widely held equity securities, designed to measure broad U.S. equity performance.
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	26.72%
Highest Quarterly Return, Date	Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text]	Worst Quarter
Lowest Quarterly Return	(22.28%)
Lowest Quarterly Return, Date	Jun. 30, 2022