Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Vanguard Variable Insurance Funds
Prospectus Date	rr_ProspectusDate	Apr. 29, 2025
Equity Index Portfolio
Risk Return Abstract	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<span style="color:#000000;font-family:Arial;font-size:13pt;font-weight:bold;">Portfolio Summary</span>
Objective [Heading]	rr_ObjectiveHeading	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Investment Objective</span>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Portfolio seeks to track the performance of a benchmark index that measures the investment return of large-capitalization stocks.
Expense [Heading]	rr_ExpenseHeading	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Fees and Expenses</span>
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses you may pay if you buy, hold, and sell shares of the Portfolio. The expenses shown in the table and in the example that follows do not reflect additional fees and expenses associated with the annuity or life insurance program through which you invest. If those additional fees and expenses were included, overall expenses would be higher.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<span style="color:#000000;font-family:Arial;font-size:8.5pt;font-weight:bold;">Annual Portfolio Operating Expenses</span> <br/><span style="color:#000000;font-family:Arial;font-size:8.5pt;">(Expenses that you pay each year as a percentage of the value of your investment)</span>
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<span style="color:#000000;font-family:Arial;font-size:9.5pt;">Portfolio Turnover</span>
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual portfolio operating expenses or in the previous expense example, reduce the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s turnover rate was 4% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	4.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#000000;font-family:Arial;font-size:9.5pt;">Example</span>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following example is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you were to invest $10,000 in the Portfolio’s shares. This example assumes that the Portfolio provides a return of 5% each year and that total annual portfolio operating expenses remain as stated in the preceding table. You would incur these hypothetical expenses whether or not you were to redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategies</span>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Vanguard Variable Insurance Funds Equity Index Portfolio (the Portfolio) employs an indexing investment approach designed to track the performance of the Standard & Poor’s 500 Index (the Index), a widely recognized benchmark of U.S. stock market performance that is dominated by the stocks of large U.S. companies. The Portfolio attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index. The Portfolio may become nondiversified, as defined under the Investment Company Act of 1940, solely as a result of an index rebalance or market movement.
Risk [Heading]	rr_RiskHeading	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Risks</span>
Risk [Text Block]	rr_RiskTextBlock	An investment in the Portfolio could lose money over short or long periods of time. You should expect the Portfolio’s share price and total return to fluctuate within a wide range. The Portfolio is subject to the following risks, which could affect the Portfolio’s performance:
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Annual Total Returns</span>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following bar chart and table are intended to help you understand the risks of investing in the Portfolio. The bar chart shows how the performance of the Portfolio has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Portfolio compare with those of its target index and another comparative index, which have investment characteristics similar to those of the Portfolio. The Portfolio’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 Portfolio’s returns, the returns would be lower. Keep in mind that the Portfolio’s past performance does not indicate how the Portfolio will perform in the future.Updated performance information is available on our website for Financial Advisors at advisors.vanguard.com.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	<span style="color:#000000;font-family:Arial;font-size:9.5pt;">The following bar chart and table are intended to help you understand the risks of investing in the Portfolio. The bar chart shows how the performance of the Portfolio has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Portfolio compare with those of its target index and another comparative index, which have investment characteristics similar to those of the Portfolio.</span>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	<span style="font-family:Arial;font-size:9.5pt;font-style:italic;">advisors.vanguard.com</span>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	<span style="color:#000000;font-family:Arial;font-size:9.5pt;"> Keep in mind that the Portfolio’s past </span><span style="font-family:Arial;font-size:9.5pt;">performance does not indicate how the Portfolio will perform in the future.</span>
Bar Chart [Heading]	rr_BarChartHeading	<span style="font-family:Arial;font-size:8pt;font-weight:bold;">Annual Total Returns — Equity Index Portfolio</span>
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	<span style="color:#000000;font-family:Arial;font-size:9.5pt;"> The Portfolio’s returns </span><span style="color:#000000;font-family:Arial;font-size:9.5pt;">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 Portfolio’s returns, the returns would be lower.</span>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest and lowest returns for a calendar quarter were:
Performance Table Heading	rr_PerformanceTableHeading	<span style="font-family:Arial;font-size:8.5pt;font-weight:bold;">Average Annual Total Returns for Periods Ended December 31, 2024</span>
Equity Index Portfolio | Risk Lose Money [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	An investment in the Portfolio could lose money over short or long periods of time.
Equity Index Portfolio | Risk Not Insured Depository Institution [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	An investment in the Portfolio is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Equity Index Portfolio | Stock Market Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Stock market risk, which is the chance that stock prices overall will decline. Stock markets tend to move in cycles, with periods of rising prices and periods of falling prices. The Portfolio’s target index tracks a subset of the U.S. stock market, which could cause the Portfolio to perform differently from the overall stock market. In addition, the Portfolio’s target index may, at times, become focused in stocks of a particular market sector, which would subject the Portfolio to proportionately higher exposure to the risks of that sector.
Equity Index Portfolio | Investment Style Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Investment style risk, which is the chance that returns from large-capitalization stocks will trail returns from the overall stock market. Large-cap stocks tend to go through cycles of doing better—or worse—than other segments of the stock market or the stock market in general. These periods have, in the past, lasted for as long as several years.
Equity Index Portfolio | index-related Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Index-related risks. The Portfolio is subject to risks associated with index investing, which include passive management risk, tracking error risk, and index provider risk. Passive management risk is the chance that the Portfolio’s use of an indexing strategy will negatively impact the Portfolio’s performance. Because the Portfolio seeks to track the performance of its target index regardless of how that index is performing, the Portfolio’s performance may be lower than it would be if the Portfolio were actively managed. Tracking error risk is the chance that the Portfolio’s performance will deviate from the performance of its target index. Tracking error risk may be heightened during times of increased market volatility or under other unusual market conditions. Index provider risk is the chance that the Portfolio will be negatively impacted by changes or errors made by the index provider. Any gains, losses, or costs associated with or resulting from an error made by the index provider will generally be borne by the Portfolio and, as a result, the Portfolio’s shareholders.
Equity Index Portfolio | Index Replicating Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Index replicating risk, which is the chance that the Portfolio may be prevented from holding one or more securities in the same proportion as in its target index.
Equity Index Portfolio | Nondiversification Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Nondiversification risk. Because the Portfolio seeks to closely track the composition of the Portfolio’s target index, from time to time, more than 25% of the Portfolio’s total assets may be invested in issuers representing more than 5% of the Portfolio’s total assets due to an index rebalance or market movement, which would result in the Portfolio being nondiversified under the Investment Company Act of 1940. The Portfolio’s performance may be hurt disproportionately by the poor performance of relatively few stocks, or even a single stock, and the Portfolio’s shares may experience significant fluctuations in value.
Equity Index Portfolio | Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	• Sector risk, which is the chance that significant problems will affect a particular sector, or that returns from that sector will trail returns from the overall stock market. Daily fluctuations in specific market sectors are often more extreme or volatile than fluctuations in the overall market. Because a significant portion of the Portfolio’s assets are invested in the information technology sector, the Portfolio’s performance is impacted by the general condition of that sector. Companies in the information technology sector could be affected by, among other things, overall economic conditions, short product cycles, rapid obsolescence of products, competition, and government regulation. Sector risk is expected to be high for the Portfolio.
Equity Index Portfolio | Equity Index Portfolio
Risk Return Abstract	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.13%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.01%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.14%
1 Year	rr_ExpenseExampleYear01	$ 14
3 Years	rr_ExpenseExampleYear03	45
5 Years	rr_ExpenseExampleYear05	79
10 Years	rr_ExpenseExampleYear10	$ 179
2015	rr_AnnualReturn2015	1.27%
2016	rr_AnnualReturn2016	11.81%
2017	rr_AnnualReturn2017	21.66%
2018	rr_AnnualReturn2018	(4.51%)
2019	rr_AnnualReturn2019	31.30%
2020	rr_AnnualReturn2020	18.20%
2021	rr_AnnualReturn2021	28.55%
Annual Return 2022	rr_AnnualReturn2022	(18.23%)
2023	rr_AnnualReturn2023	26.11%
2024	rr_AnnualReturn2024	24.84%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	<span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Highest</span>
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2020
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	20.53%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	<span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Lowest</span>
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2020
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(19.66%)
1 Year	rr_AverageAnnualReturnYear01	24.84%
5 Years	rr_AverageAnnualReturnYear05	14.36%
10 Years	rr_AverageAnnualReturnYear10	12.95%
Equity Index Portfolio | Dow Jones U.S. Total Stock Market Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	23.88%
5 Years	rr_AverageAnnualReturnYear05	13.78%
10 Years	rr_AverageAnnualReturnYear10	12.48%
Equity Index Portfolio | Standard & Poor's 500 Index (reflects no deduction for fees, expenses, or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	25.02%
5 Years	rr_AverageAnnualReturnYear05	14.53%
10 Years	rr_AverageAnnualReturnYear10	13.10%