Small Cap Index Trust Performance Management - Small Cap Index Trust	Dec. 31, 2025
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	<span style="color:#000000;font-family:Arial Narrow;font-size:10pt;font-weight:bold;">Past performance</span>
Performance Narrative [Text Block]	The following information illustrates the variability of the fund’s returns and provides some indication of the risks of investing in the fund by showing changes in the fund’s performance from year to year and by showing how the fund’s average annual returns compared with a broad-based securities market index. Past performance does not indicate future results. The Russell 2000 Index shows how the fund’s performance compares against the returns of similar investments. All figures assume dividend reinvestment. The performance information below does not reflect fees and expenses of any variable insurance contract which may use JHVIT as its underlying investment option. If such fees and expenses had been reflected, performance would be lower.
Performance Past Does Not Indicate Future [Text]	<span style="color:#000000;font-family:Arial Narrow;font-size:9pt;">Past performance does not indicate future results.</span>
Performance Information Illustrates Variability of Returns [Text]	<span style="color:#000000;font-family:Arial Narrow;font-size:9pt;">The following information illustrates the variability of the fund’s returns and provides some indication of the risks of investing in the fund by showing changes in the fund’s performance from year to year and by showing how the fund’s average annual returns compared with a broad-based securities market index. </span>
Bar Chart [Heading]	<span style="font-family:Arial Narrow;font-size:9pt;font-weight:bold;">Calendar year total returns (%)—Series I</span>
Bar Chart Closing [Text Block]	Best quarter:Q4 202031.14%Worst quarter:Q1 2020-30.72%
Performance Table Heading	<span style="font-family:Arial Narrow;font-size:8pt;font-weight:bold;margin-left:0.0pt;">Average annual total returns (%)—as of 12/31/2025</span>
Series I
Prospectus [Line Items]
Highest Quarterly Return, Label [Optional Text]	<span style="color:#000000;font-family:Arial Narrow;font-size:8pt;font-weight:bold;margin-left:0.0pt;">Best quarter:</span>
Highest Quarterly Return	31.14%
Highest Quarterly Return, Date	Dec. 31, 2020
Lowest Quarterly Return, Label [Optional Text]	<span style="color:#000000;font-family:Arial Narrow;font-size:8pt;font-weight:bold;margin-left:0.0pt;">Worst quarter:</span>
Lowest Quarterly Return	(30.72%)
Lowest Quarterly Return, Date	Mar. 31, 2020