Equity Index Portfolio Performance Management - Portfolio [Member] - Equity Index Portfolio |
Dec. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Annual Total Returns</span> |
| Performance Narrative [Text Block] | The following bar chart and table show the Fund’s historical performance and are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund compare with those of a broad-based securities market index and one or more additional indexes with similar investment characteristics as the Fund. The Fund’s returns are net of its expenses, but do not reflect additional fees and expenses that are deducted by the annuity or life insurance program through which you invest. If such fees and expenses were included in the calculation of the Fund’s returns, the returns would be lower.Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website for Financial Advisors at advisors.vanguard.com. |
| Performance Past Does Not Indicate Future [Text] | <span style="font-family:Arial;font-size:9.5pt;">Keep in mind that the Fund’s past performance does not indicate how the Fund will perform in the future.</span> |
| Performance Information Illustrates Variability of Returns [Text] | <span style="font-family:Arial;font-size:9.5pt;">The following bar chart and table show the Fund’s historical performance and are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund compare with those of a broad-based securities market index and one or more</span><span style="font-family:Arial;font-size:9.5pt;line-height:11.5pt;"> </span><span style="font-family:Arial;font-size:9.5pt;">additional indexes with similar investment characteristics as the Fund.</span> |
| Bar Chart Does Not Reflect Sales Loads [Text] | <span style="font-family:Arial;font-size:9.5pt;"> The Fund’s returns are net of its expenses, but do </span><span style="font-family:Arial;font-size:9.5pt;">not reflect additional fees and expenses that are deducted by the annuity or life insurance program through which you invest. If such fees and expenses were included in the calculation of the Fund’s returns, the returns would be lower.</span> |
| Bar Chart [Heading] | <span style="font-family:Arial;font-size:8pt;font-weight:bold;">Annual Total Returns — Equity Index Portfolio</span> |
| Bar Chart Closing [Text Block] | During the periods shown in the bar chart, the highest and lowest returns for a calendar quarter were: |
| Performance Table Heading | <span style="font-family:Arial;font-size:8.5pt;font-weight:bold;">Average Annual Total Returns for Periods Ended December 31, 2025</span> |
| Performance Availability Website Address [Text] | <span style="font-family:Arial;font-size:9.5pt;font-style:italic;">advisors.vanguard.com</span> |
| Equity Index Portfolio | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | <span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Highest</span> |
| Highest Quarterly Return | 20.53% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | <span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Lowest</span> |
| Lowest Quarterly Return | (19.66%) |
| Lowest Quarterly Return, Date | Mar. 31, 2020 |