Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Retail | Vanguard Short-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide current income while maintaining limited price volatility.
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 Investor Shares or Admiral Shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (Fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund 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 Fund 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 and may result in more taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the previous expense examples, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 75% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	75.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	Examples
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following examples are intended to help you compare the cost of investing in the Fund’s Investor Shares or Admiral Shares with the cost of investing in other mutual funds. They illustrate the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. These examples assume that the Shares provide a return of 5% each year and that total annual fund operating expenses 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 Fund invests in a variety of high-quality and, to a lesser extent, medium-quality fixed income securities, at least 80% of which will be short- and intermediate-term investment-grade securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc., or another independent rating agency or, if unrated, are determined to be of comparable quality by the Fund’s advisor; medium-quality fixed income securities are those rated the equivalent of Baa1, Baa2, or Baa3 by Moody‘s or another independent rating agency or, if unrated, are determined to be of comparable quality by the Fund’s advisor. (Investment-grade fixed income securities are those rated the equivalent of Baa3 and above by Moody’s or another independent rating agency or, if unrated, are determined to be of comparable quality by the Fund’s advisor.) The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The Fund is designed for investors with a low tolerance for risk, but you could still lose money by investing in it. The Fund is subject to the following risks, which could affect the Fund’s performance: • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally high for short-term bond funds, so investors should expect the Fund’s monthly income to fluctuate. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be low for the Fund because it invests primarily in short-term bonds, whose prices are less sensitive to interest rate changes than are the prices of longer-term bonds. • Credit risk, which is the chance that a bond issuer 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 bond to decline. Although the Fund invests a limited portion of its assets in low-quality bonds, credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality and, to a lesser extent, in bonds that are considered medium-quality. • 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. The 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 Fund’s income. Such redemptions and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Call risk should be low for the Fund. • Extension risk, which is the chance that during periods of rising interest rates, certain debt securities will be paid off substantially more slowly than originally anticipated, and the value of those securities may fall. Extension risk is generally low for short-term bond funds. • Liquidity risk, which is the chance that the Fund may not be able to sell a security in a timely manner at a desired price. Liquidity risk is generally low for short-term corporate bonds. • Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective. • Derivatives risk. The Fund may invest in derivatives, which may involve risks different from, and possibly greater than, those of investments directly in the underlying securities or assets. An investment in the Fund 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 Fund is designed for investors with a low tolerance for risk, but you could still lose money by investing in it.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the Fund 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 Fund. The bar chart shows how the performance of the Fund‘s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index, which has investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.
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 Fund. The bar chart shows how the performance of the Fund‘s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index, which has investment characteristics similar to those of the Fund.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-662-7447
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	vanguard.com/performance
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Short-Term Investment-Grade Fund Investor Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 6.02% (quarter ended June 30, 2009), and the lowest return for a quarter was –3.42% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	When after-tax returns are calculated, it is assumed that the shareholder was in the highest individual federal marginal income tax bracket at the time of each distribution of income or capital gains or upon redemption. State and local income taxes are not reflected in the calculations.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant for a shareholder who holds fund shares in a tax-deferred account, such as an individual retirement account or a 401(k) plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	Please note that after-tax returns are shown only for the Investor Shares and may differ for each share class.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	Also, figures captioned Return After Taxes on Distributions and Sale of Fund Shares may be higher than other figures for the same period if a capital loss occurs upon redemption and results in an assumed tax deduction for the shareholder.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	Actual after-tax returns depend on your tax situation and may differ from those shown in the preceding table. When after-tax returns are calculated, it is assumed that the shareholder was in the highest individual federal marginal income tax bracket at the time of each distribution of income or capital gains or upon redemption. State and local income taxes are not reflected in the calculations. Please note that after-tax returns are shown only for the Investor Shares and may differ for each share class. After-tax returns are not relevant for a shareholder who holds fund shares in a tax-deferred account, such as an individual retirement account or a 401(k) plan. Also, figures captioned Return After Taxes on Distributions and Sale of Fund Shares may be higher than other figures for the same period if a capital loss occurs upon redemption and results in an assumed tax deduction for the shareholder.
Retail | Vanguard Short-Term Investment-Grade Fund | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
Purchase Fee	rr_MaximumCumulativeSalesChargeOverOther	none
Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee	rr_RedemptionFeeOverRedemption	none
Account Service Fee (for certain fund account balances below $10,000)	rr_MaximumAccountFee	$ 20	[1]
Management Fees	rr_ManagementFeesOverAssets	0.17%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.20%
1 Year	rr_ExpenseExampleYear01	$ 20
3 Years	rr_ExpenseExampleYear03	64
5 Years	rr_ExpenseExampleYear05	113
10 Years	rr_ExpenseExampleYear10	255
1 Year	rr_ExpenseExampleNoRedemptionYear01	20
3 Years	rr_ExpenseExampleNoRedemptionYear03	64
5 Years	rr_ExpenseExampleNoRedemptionYear05	113
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 255
2006	rr_AnnualReturn2006	4.99%	[2]
2007	rr_AnnualReturn2007	5.86%	[2]
2008	rr_AnnualReturn2008	(4.74%)	[2]
2009	rr_AnnualReturn2009	14.03%	[2]
2010	rr_AnnualReturn2010	5.21%	[2]
2011	rr_AnnualReturn2011	1.93%	[2]
2012	rr_AnnualReturn2012	4.52%	[2]
2013	rr_AnnualReturn2013	0.97%	[2]
2014	rr_AnnualReturn2014	1.76%	[2]
2015	rr_AnnualReturn2015	1.03%	[2]
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2016
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	1.74%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.02%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.42%)
1 Year	rr_AverageAnnualReturnYear01	1.03%
5 Years	rr_AverageAnnualReturnYear05	2.04%
10 Years	rr_AverageAnnualReturnYear10	3.46%
Retail | Vanguard Short-Term Investment-Grade Fund | Admiral Shares
Risk/Return:	rr_RiskReturnAbstract
Purchase Fee	rr_MaximumCumulativeSalesChargeOverOther	none
Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee	rr_RedemptionFeeOverRedemption	none
Account Service Fee (for certain fund account balances below $10,000)	rr_MaximumAccountFee	$ 20	[1]
Management Fees	rr_ManagementFeesOverAssets	0.09%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.10%
1 Year	rr_ExpenseExampleYear01	$ 10
3 Years	rr_ExpenseExampleYear03	32
5 Years	rr_ExpenseExampleYear05	56
10 Years	rr_ExpenseExampleYear10	128
1 Year	rr_ExpenseExampleNoRedemptionYear01	10
3 Years	rr_ExpenseExampleNoRedemptionYear03	32
5 Years	rr_ExpenseExampleNoRedemptionYear05	56
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 128
1 Year	rr_AverageAnnualReturnYear01	1.13%
5 Years	rr_AverageAnnualReturnYear05	2.13%
10 Years	rr_AverageAnnualReturnYear10	3.56%
Retail | Vanguard Short-Term Investment-Grade Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.17%
5 Years	rr_AverageAnnualReturnYear05	1.11%
10 Years	rr_AverageAnnualReturnYear10	2.22%
Retail | Vanguard Short-Term Investment-Grade Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.58%
5 Years	rr_AverageAnnualReturnYear05	1.21%
10 Years	rr_AverageAnnualReturnYear10	2.21%
Retail | Vanguard Short-Term Investment-Grade Fund | Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.06%
5 Years	rr_AverageAnnualReturnYear05	2.55%
10 Years	rr_AverageAnnualReturnYear10	4.07%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.74%.