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Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName VANGUARD VARIABLE INSURANCE FUNDS
Prospectus Date rr_ProspectusDate Apr. 28, 2017
Conservative Allocation Portfolio  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Conservative Allocation Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The Portfolio seeks to provide current income and low to moderate capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses you may pay if you buy and hold shares of the Portfolio. The expenses shown in the table and in the example that follow 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 Annual Portfolio Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Portfolio may pay transaction costs, such as purchase fees, 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 14% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 14.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The following example is intended to help you compare the cost of investing in the Portfolio (based on the fees and expenses of the underlying funds) 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 operating expenses of the Portfolio and its underlying funds remain as stated in the preceding table. You would incur these hypothetical expenses whether or not you 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 Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock The Portfolio invests in a mix of Vanguard mutual funds and other portfolios of Vanguard Variable Insurance Fund (collectively, the underlying funds) according to an asset-allocation strategy that reflects an allocation of approximately 60% of the Portfolio’s assets to fixed-income securities and 40% to common stocks. The targeted percentage of the Portfolio’s assets allocated to the underlying asset classes is:

• U.S. fixed-income securities 42%
• Large-cap U.S. stocks 19%
• Foreign stocks 16%
• Foreign fixed-income securities 18%
• Small- and mid-cap U.S. stocks 5%

The Portfolio’s indirect fixed-income holdings are a diversified mix of short-, intermediate-, and long-term U.S. government, U.S. agency, and investment-grade U.S. corporate bonds; mortgage-backed and asset-backed securities; and government, agency, corporate, and investment-grade foreign bonds issued in currencies other than the U.S. dollar (but hedged by Vanguard, typically with foreign currency exchange forward contracts, to minimize foreign currency exposure). The Portfolio’s indirect stock holdings are a diversified mix of U.S. and foreign large-, mid-, and small-capitalization stocks.

The Portfolio uses its investment in large-cap U.S. stocks and small- and mid-cap U.S. stocks to gain exposure to the overall domestic stock market. While the percentage of the Portfolio’s assets invested in either of these two asset classes may deviate slightly from the target allocation, the combination of the two asset classes will equal approximately 24% of the Portfolio’s assets in the aggregate.

The Portfolio’s board of trustees may change the targeted allocation to the underlying asset classes without shareholder approval.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock The Portfolio is subject to the risks associated with the stock and bond markets, any of which could cause an investor to lose money. However, because fixed-income securities such as bonds usually are less volatile than stocks and because the Portfolio invests more than half of its assets in fixed-income securities, the Portfolio’s overall level of risk should be low to moderate.

• With a target allocation of approximately 60% of its assets to fixed-income securities, the Portfolio is proportionately subject to bond risks, including the following: interest rate risk, which is the chance that bond prices will decline because of rising interest rates; credit risk, which is the chance that the issuer of a security will fail to pay interest or principal in a timely manner, or that negative perceptions of the issuer’s ability to make such payments will cause the price of that security to decline, thus reducing the underlying fund’s return; and income risk, which is the chance that an underlying fund’s income will decline because of falling interest rates. If an underlying fund holds securities that are callable, the underlying fund’s income may decline because of call risk, which is the chance that during periods of falling interest rates, issuers of callable bonds may call (redeem) securities with higher coupon rates or interest rates before their maturity dates. An underlying fund would then lose any price appreciation above the bond’s call price and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the underlying fund’s income. Such redemptions and subsequent reinvestments would also increase the Portfolio’s turnover rate. For mortgage-backed securities, this risk is known as prepayment risk. The Portfolio is also subject to the following risks associated with investments in currency-hedged foreign bonds: country/regional risk, which is the chance that world events—such as political upheaval, financial troubles, or natural disasters—will adversely affect the value and/or liquidity of securities issued by foreign governments, government agencies, or companies; and currency hedging risk, which is the chance that the currency hedging transactions entered into by the underlying foreign fixed-income securities fund may not perfectly offset the fund’s foreign currency exposure.

• With approximately 40% of its assets allocated to stocks, the Portfolio is proportionately subject to 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 is also subject to the following risks associated with investments in foreign stocks: country/regional risk, which is the chance that world events—such as political upheaval, financial troubles, or natural disasters—will adversely affect the value of securities issued by companies in foreign countries or regions; and currency risk, which is the chance that the value of a foreign investment, measured in U.S. dollars, will decrease because of unfavorable changes in currency exchange rates. Country/regional risk and currency risk are especially high in emerging markets.

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.
Risk Lose Money [Text] rr_RiskLoseMoney The Portfolio is subject to the risks associated with the stock and bond markets, any of which could cause an investor to lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Annual Total Returns
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 a relevant market index and other comparative benchmarks, 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. Returns for the Variable Insurance Mixed-Asset Target Allocation Conservative Funds Average are derived from data provided by Lipper, a Thomson Reuters Company. 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 or by calling Vanguard toll-free at 800-522-5555.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns 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 a relevant market index and other comparative benchmarks, which have investment characteristics similar to those of the Portfolio.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 800-522-5555
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress advisors.vanguard.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Keep in mind that the Portfolio’s past performance does not indicate how the Portfolio will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns — Conservative Allocation Portfolio
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads 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.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock During the periods shown in the bar chart, the highest return for a calendar quarter was 5.03% (quarter ended March 31, 2012), and the lowest return for a quarter was –2.63% (quarter ended September 30, 2015).
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns for Periods Ended December 31, 2016
Conservative Allocation Portfolio | Conservative Allocation Portfolio  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets none
12b-1 Distribution Fee rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets none
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.16%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 0.16%
1 Year rr_ExpenseExampleYear01 $ 16
3 Years rr_ExpenseExampleYear03 52
5 Years rr_ExpenseExampleYear05 90
10 Years rr_ExpenseExampleYear10 205
1 Year rr_ExpenseExampleNoRedemptionYear01 16
3 Years rr_ExpenseExampleNoRedemptionYear03 52
5 Years rr_ExpenseExampleNoRedemptionYear05 90
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 205
2012 rr_AnnualReturn2012 9.25%
2013 rr_AnnualReturn2013 9.06%
2014 rr_AnnualReturn2014 6.91%
2015 rr_AnnualReturn2015 0.20%
2016 rr_AnnualReturn2016 6.02%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.03%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.63%)
1 Year rr_AverageAnnualReturnYear01 6.02%
5 Years rr_AverageAnnualReturnYear05 6.24%
Since Inception rr_AverageAnnualReturnSinceInception 6.43%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 19, 2011
Conservative Allocation Portfolio | Bloomberg Barclays U.S. Aggregate Float Adjusted Index  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 2.75% [1]
5 Years rr_AverageAnnualReturnYear05 2.24% [1]
Since Inception rr_AverageAnnualReturnSinceInception 13.46% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 19, 2011 [1]
Conservative Allocation Portfolio | Conservative Allocation Composite Index  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 6.27% [1]
5 Years rr_AverageAnnualReturnYear05 6.44% [1]
Since Inception rr_AverageAnnualReturnSinceInception 6.61% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 19, 2011 [1]
Conservative Allocation Portfolio | Variable Insurance Mixed-Asset Target Allocation Conservative Funds Average  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 5.22% [1]
5 Years rr_AverageAnnualReturnYear05 4.86% [1]
Since Inception rr_AverageAnnualReturnSinceInception 5.08% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 19, 2011 [1]
[1] Comparative Benchmarks (reflect no deduction for fees or expenses)