485BPOS

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form N-1A
REGISTRATION STATEMENT (NO. 2-47371)
UNDER THE SECURITIES ACT OF 1933	[X]
Pre-Effective Amendment No.	[ ]
Post-Effective Amendment No. 110	[X]
and

REGISTRATION STATEMENT (NO. 811-2368) UNDER THE INVESTMENT COMPANY ACT

OF 1940

Amendment No. 111

[X]

VANGUARD FIXED INCOME SECURITIES FUNDS

(Exact Name of Registrant as Specified in Declaration of Trust)

P.O. Box 2600, Valley Forge, PA 19482 (Address of Principal Executive Office)

Registrant’s Telephone Number (610) 669-1000

Heidi Stam, Esquire
P.O. Box 876
Valley Forge, PA 19482

It is proposed that this filing will become effective (check appropriate box)

[X] immediately upon filing pursuant to paragraph (b)

[ ] on (date) pursuant to paragraph (b)

[ ] 60 days after filing pursuant to paragraph (a)(1)

[ ] on (date), pursuant to paragraph (a)(1)

[ ] 75 days after filing pursuant to paragraph (a)(2)

[ ] on (date) pursuant to paragraph (a)(2) of rule 485

If appropriate, check the following box:

[ ] This post-effective amendment designates a new effective date for a

previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant hereby certifies that it meets all requirements for effectiveness of this Registration Statements pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the Town of Valley Forge and the Commonwealth of Pennsylvania, on the 8th day of June, 2016.

VANGUARD FIXED INCOME SECURITIES FUNDS

BY: /s/ F. William McNabb III*

F. William McNabb III
Chairman and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated:

/s/ F. William McNabb III*	Chairman and Chief Executive	June 8, 2016
	Officer
F. William McNabb III
/s/ Emerson U. Fullwood*	Trustee	June 8, 2016
Emerson U. Fullwood
/s/ Rajiv L. Gupta*	Trustee	June 8, 2016
Rajiv L. Gupta
/s/ Amy Gutmann*	Trustee	June 8, 2016
Amy Gutmann
/s/ JoAnn Heffernan Heisen*	Trustee	June 8, 2016
JoAnn Heffernan Heisen
/s/ F. Joseph Loughrey*	Trustee	June 8, 2016
F. Joseph Loughrey
/s/ Mark Loughridge*	Trustee	June 8, 2016
Mark Loughridge
/s/ Scott C. Malpass*	Trustee	June 8, 2016
Scott C. Malpass
/s/ André F. Perold*	Trustee	June 8, 2016
André F. Perold
/s/ Peter F. Volanakis*	Trustee	June 8, 2016
Peter F. Volanakis
/s/ Thomas J. Higgins*	Chief Financial Officer	June 8, 2016
Thomas J. Higgins

*By: /s/ Heidi Stam

Heidi Stam, pursuant to a Power of Attorney filed on April 22, 2014, see File Number 2-17620, Incorporated by Reference.

INDEX TO EXHIBITS
XBRL Instance Document	Ex-101.INS
XBRL Taxonomy Extension Schema Document	Ex-101.SCH
XBRL Taxonomy Extension Calculation Linkbase Document	Ex-101.CAL
XBRL Taxonomy Extension Definition Linkbase Document.	Ex-101.DEF
XBRL Taxonomy Extension Labels Linkbase Document	Ex-101.LAB
XBRL Taxonomy Extension Presentation Linkbase Document	Ex-101.PRE

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Jan. 31, 2016
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Central Index Key	dei_EntityCentralIndexKey	0000106444
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	May 26, 2016
Document Effective Date	dei_DocumentEffectiveDate	May 26, 2016
Prospectus Date	rr_ProspectusDate	May 26, 2016

XML

Institutional | Vanguard Short-Term Investment-Grade Fund

Fund Summary

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Institutional Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Institutional Vanguard Short-Term Investment-Grade Fund Institutional Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Institutional Vanguard Short-Term Investment-Grade Fund Institutional Shares
Management Fees	0.06%
12b-1 Distribution Fee	none
Other Expenses	0.01%
Total Annual Fund Operating Expenses	0.07%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Institutional Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Institutional | Vanguard Short-Term Investment-Grade Fund | Institutional Shares | USD ($)	7	23	40	90

Portfolio Turnover

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 example, 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.

Principal Investment Strategies

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.

Principal Risks

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.

Annual Total Returns

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 Institutional Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Institutional Shares 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.

Annual Total Returns — Vanguard Short-Term Investment-Grade Fund Institutional Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 6.06% (quarter ended June 30, 2009), and the lowest return for a quarter was –3.39% (quarter ended September 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Institutional - Vanguard Short-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Institutional Shares	1.16%	2.17%	3.60%
Institutional Shares | Return After Taxes on Distributions	0.24%	1.19%	2.31%
Institutional Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.66%	1.29%	2.30%
Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees, expenses, or taxes)	1.06%	2.55%	4.07%

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 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.

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.77%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Institutional | Vanguard Short-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
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 Institutional 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 example, 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	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following example is intended to help you compare the cost of investing in the Fund’s Institutional Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 Institutional Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Institutional Shares 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 Institutional Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Institutional Shares 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 Institutional Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 6.06% (quarter ended June 30, 2009), and the lowest return for a quarter was –3.39% (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	Please note that 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 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 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.
Institutional | Vanguard Short-Term Investment-Grade Fund | Institutional 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
Management Fees	rr_ManagementFeesOverAssets	0.06%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.07%
1 Year	rr_ExpenseExampleYear01	$ 7
3 Years	rr_ExpenseExampleYear03	23
5 Years	rr_ExpenseExampleYear05	40
10 Years	rr_ExpenseExampleYear10	90
1 Year	rr_ExpenseExampleNoRedemptionYear01	7
3 Years	rr_ExpenseExampleNoRedemptionYear03	23
5 Years	rr_ExpenseExampleNoRedemptionYear05	40
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 90
2006	rr_AnnualReturn2006	5.14%	[1]
2007	rr_AnnualReturn2007	6.01%	[1]
2008	rr_AnnualReturn2008	(4.61%)	[1]
2009	rr_AnnualReturn2009	14.21%	[1]
2010	rr_AnnualReturn2010	5.37%	[1]
2011	rr_AnnualReturn2011	2.06%	[1]
2012	rr_AnnualReturn2012	4.66%	[1]
2013	rr_AnnualReturn2013	1.10%	[1]
2014	rr_AnnualReturn2014	1.90%	[1]
2015	rr_AnnualReturn2015	1.16%	[1]
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	1.77%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.06%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.39%)
1 Year	rr_AverageAnnualReturnYear01	1.16%
5 Years	rr_AverageAnnualReturnYear05	2.17%
10 Years	rr_AverageAnnualReturnYear10	3.60%
Institutional | Vanguard Short-Term Investment-Grade Fund | Return After Taxes on Distributions | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.24%
5 Years	rr_AverageAnnualReturnYear05	1.19%
10 Years	rr_AverageAnnualReturnYear10	2.31%
Institutional | Vanguard Short-Term Investment-Grade Fund | Return After Taxes on Distributions and Sale of Fund Shares | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.66%
5 Years	rr_AverageAnnualReturnYear05	1.29%
10 Years	rr_AverageAnnualReturnYear10	2.30%
Institutional | 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] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.77%.

XML

Retail | Vanguard Ultra-Short-Term Bond Fund

Fund Summary

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Ultra-Short-Term Bond Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Ultra-Short-Term Bond Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.09%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.03%
Total Annual Fund Operating Expenses	0.20%	0.12%

Examples

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:

Expense Example - Retail - Vanguard Ultra-Short-Term Bond Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	12	39	68	154

Portfolio Turnover

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 fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests in a diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.

Principal Risks

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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality.

• 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 should be low for the Fund, because it invests only a portion of its assets in 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.

Annual Total Returns

The Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

[1] /year

XML

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 Ultra-Short-Term Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
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 fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	24.00%
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 diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.
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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality. • 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 should be low for the Fund, because it invests only a portion of its assets in 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 Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not been in operation long enough to report a full calendar-year return.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-662-7447
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	vanguard.com/performance
Retail | Vanguard Ultra-Short-Term Bond 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
Retail | Vanguard Ultra-Short-Term Bond 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	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.12%
1 Year	rr_ExpenseExampleYear01	$ 12
3 Years	rr_ExpenseExampleYear03	39
5 Years	rr_ExpenseExampleYear05	68
10 Years	rr_ExpenseExampleYear10	154
1 Year	rr_ExpenseExampleNoRedemptionYear01	12
3 Years	rr_ExpenseExampleNoRedemptionYear03	39
5 Years	rr_ExpenseExampleNoRedemptionYear05	68
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 154

[1] /year

XML

Investor Shares for Participants | Vanguard Ultra-Short-Term Bond Fund

Fund Summary

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Ultra-Short-Term Bond Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Ultra-Short-Term Bond Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Ultra-Short-Term Bond Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests in a diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.

Principal Risks

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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality.

• 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 should be low for the Fund, because it invests only a portion of its assets in 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.

Annual Total Returns

The Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Ultra-Short-Term Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
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 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 example, reduce the Fund’s performance. During the fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	24.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.
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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality. • 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 should be low for the Fund, because it invests only a portion of its assets in 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 Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not been in operation long enough to report a full calendar-year return.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-662-7447
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	vanguard.com/performance
Investor Shares for Participants | Vanguard Ultra-Short-Term Bond 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
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

XML

Admiral Shares for Participants | Vanguard Ultra-Short-Term Bond Fund

Fund Summary

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Ultra-Short-Term Bond Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Ultra-Short-Term Bond Fund Admiral Shares
Management Fees	0.09%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.12%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Ultra-Short-Term Bond Fund | Admiral Shares | USD ($)	12	39	68	154

Portfolio Turnover

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 example, reduce the Fund’s performance. During the fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests in a diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.

Principal Risks

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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality.

• 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 should be low for the Fund, because it invests only a portion of its assets in 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.

Annual Total Returns

The Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Ultra-Short-Term Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
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 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 example, reduce the Fund’s performance. During the fiscal period from February 24, 2015, to January 31, 2016, the Fund’s portfolio turnover rate was 24% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	24.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 diversified portfolio of high-quality and, to a lesser extent, medium-quality fixed income securities. High-quality fixed income securities are those rated the equivalent of A3 or better by Moody‘s Investors Service, Inc. (Moody‘s) 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. The Fund may invest no more than 30% of its assets in medium-quality fixed income securities. The Fund is expected to maintain a dollar-weighted average maturity of 0 to 2 years. Under normal circumstances, the Fund will invest at least 80% of its assets in fixed income securities.
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. Credit risk should be low for the Fund because it invests primarily in bonds that are considered high-quality. • 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 should be low for the Fund, because it invests only a portion of its assets in 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 Fund has not been in operation long enough to report a full calendar-year return. Performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund has not been in operation long enough to report a full calendar-year return.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800-662-7447
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	vanguard.com/performance
Admiral Shares for Participants | Vanguard Ultra-Short-Term Bond 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
Management Fees	rr_ManagementFeesOverAssets	0.09%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.12%
1 Year	rr_ExpenseExampleYear01	$ 12
3 Years	rr_ExpenseExampleYear03	39
5 Years	rr_ExpenseExampleYear05	68
10 Years	rr_ExpenseExampleYear10	154
1 Year	rr_ExpenseExampleNoRedemptionYear01	12
3 Years	rr_ExpenseExampleNoRedemptionYear03	39
5 Years	rr_ExpenseExampleNoRedemptionYear05	68
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 154

XML

Retail | Vanguard High-Yield Corporate Fund

Fund Summary

Investment Objective

The Fund seeks to provide a high level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard High-Yield Corporate Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard High-Yield Corporate Fund	Investor Shares	Admiral Shares
Management Fees	0.20%	0.12%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.01%
Total Annual Fund Operating Expenses	0.23%	0.13%

Examples

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:

Expense Example - Retail - Vanguard High-Yield Corporate Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	24	74	130	293
Admiral Shares	13	42	73	166

Portfolio Turnover

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 34% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor.

The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings.

• 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• 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 moderate for the Fund because it invests only a portion of its assets in callable bonds.

• Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 and loans and moderate for intermediate-term corporate bonds and loans.

• 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.

Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares.

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.

Annual Total Returns

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 and a composite index, which have 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.

Annual Total Returns — Vanguard High-Yield Corporate Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 14.43% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.94% (quarter ended December 31, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard High-Yield Corporate Fund		1 Year	5 Years	10 Years
Investor Shares		(1.39%)	5.72%	6.02%
Investor Shares | Return After Taxes on Distributions		(3.86%)	3.20%	3.35%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares		(0.65%)	3.38%	3.56%
Admiral Shares		(1.30%)	5.83%	6.14%
Barclays U.S. Corporate High Yield Bond Index	[1]	(4.47%)	5.04%	6.96%
High-Yield Corporate Composite Index	[1]	(2.53%)	5.23%	6.41%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.30%.

[1] Comparative Indexes (reflect no deduction for fees, expenses, or taxes)

XML

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 High-Yield Corporate Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high level of current income.
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 34% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	34.00%
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 primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings. • 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • 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 moderate for the Fund because it invests only a portion of its assets in callable bonds. • Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 and loans and moderate for intermediate-term corporate bonds and loans. • 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. Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares. 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	An investment in the Fund could lose money over short or even long periods.
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 and a composite index, which have 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 and a composite index, which have 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 High-Yield Corporate 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 14.43% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.94% (quarter ended December 31, 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 High-Yield Corporate 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	0.20%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.23%
1 Year	rr_ExpenseExampleYear01	$ 24
3 Years	rr_ExpenseExampleYear03	74
5 Years	rr_ExpenseExampleYear05	130
10 Years	rr_ExpenseExampleYear10	293
1 Year	rr_ExpenseExampleNoRedemptionYear01	24
3 Years	rr_ExpenseExampleNoRedemptionYear03	74
5 Years	rr_ExpenseExampleNoRedemptionYear05	130
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 293
2006	rr_AnnualReturn2006	8.24%	[2]
2007	rr_AnnualReturn2007	2.04%	[2]
2008	rr_AnnualReturn2008	(21.29%)	[2]
2009	rr_AnnualReturn2009	39.09%	[2]
2010	rr_AnnualReturn2010	12.40%	[2]
2011	rr_AnnualReturn2011	7.13%	[2]
2012	rr_AnnualReturn2012	14.36%	[2]
2013	rr_AnnualReturn2013	4.54%	[2]
2014	rr_AnnualReturn2014	4.58%	[2]
2015	rr_AnnualReturn2015	(1.39%)	[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	2.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	14.43%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(13.94%)
1 Year	rr_AverageAnnualReturnYear01	(1.39%)
5 Years	rr_AverageAnnualReturnYear05	5.72%
10 Years	rr_AverageAnnualReturnYear10	6.02%
Retail | Vanguard High-Yield Corporate 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	0.12%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.13%
1 Year	rr_ExpenseExampleYear01	$ 13
3 Years	rr_ExpenseExampleYear03	42
5 Years	rr_ExpenseExampleYear05	73
10 Years	rr_ExpenseExampleYear10	166
1 Year	rr_ExpenseExampleNoRedemptionYear01	13
3 Years	rr_ExpenseExampleNoRedemptionYear03	42
5 Years	rr_ExpenseExampleNoRedemptionYear05	73
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 166
1 Year	rr_AverageAnnualReturnYear01	(1.30%)
5 Years	rr_AverageAnnualReturnYear05	5.83%
10 Years	rr_AverageAnnualReturnYear10	6.14%
Retail | Vanguard High-Yield Corporate Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(3.86%)
5 Years	rr_AverageAnnualReturnYear05	3.20%
10 Years	rr_AverageAnnualReturnYear10	3.35%
Retail | Vanguard High-Yield Corporate Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(0.65%)
5 Years	rr_AverageAnnualReturnYear05	3.38%
10 Years	rr_AverageAnnualReturnYear10	3.56%
Retail | Vanguard High-Yield Corporate Fund | Barclays U.S. Corporate High Yield Bond Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(4.47%)	[3]
5 Years	rr_AverageAnnualReturnYear05	5.04%	[3]
10 Years	rr_AverageAnnualReturnYear10	6.96%	[3]
Retail | Vanguard High-Yield Corporate Fund | High-Yield Corporate Composite Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(2.53%)	[3]
5 Years	rr_AverageAnnualReturnYear05	5.23%	[3]
10 Years	rr_AverageAnnualReturnYear10	6.41%	[3]

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.30%.

[3] Comparative Indexes (reflect no deduction for fees, expenses, or taxes)

XML

Investor Shares for Participants | Vanguard High-Yield Corporate Fund

Fund Summary

Investment Objective

The Fund seeks to provide a high level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard High-Yield Corporate Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard High-Yield Corporate Fund Investor Shares
Management Fees	0.20%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.23%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard High-Yield Corporate Fund | Investor Shares | USD ($)	24	74	130	293

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 34% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor.

The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings.

• 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• 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 moderate for the Fund because it invests only a portion of its assets in callable bonds.

• Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 and loans and moderate for intermediate-term corporate bonds and loans.

• 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.

Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares.

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.

Annual Total Returns

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 Investor Shares compare with those of a relevant market index and a composite index, which have investment characteristics similar to those of the Fund. 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 at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns — Vanguard High-Yield Corporate Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 14.43% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.94% (quarter ended December 31, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard High-Yield Corporate Fund		1 Year	5 Years	10 Years
Investor Shares		(1.39%)	5.72%	6.02%
Barclays U.S. Corporate High Yield Bond Index	[1]	(4.47%)	5.04%	6.96%
High-Yield Corporate Composite Index	[1]	(2.53%)	5.23%	6.41%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.30%.

[1] Comparative Indexes (reflect no deduction for fees or expenses)

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard High-Yield Corporate Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 34% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	34.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings. • 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • 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 moderate for the Fund because it invests only a portion of its assets in callable bonds. • Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 and loans and moderate for intermediate-term corporate bonds and loans. • 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. Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares. 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares compare with those of a relevant market index and a composite index, which have investment characteristics similar to those of the Fund. 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 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 Investor Shares compare with those of a relevant market index and a composite index, which have 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard High-Yield Corporate 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 14.43% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.94% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard High-Yield Corporate 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
Management Fees	rr_ManagementFeesOverAssets	0.20%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.23%
1 Year	rr_ExpenseExampleYear01	$ 24
3 Years	rr_ExpenseExampleYear03	74
5 Years	rr_ExpenseExampleYear05	130
10 Years	rr_ExpenseExampleYear10	293
1 Year	rr_ExpenseExampleNoRedemptionYear01	24
3 Years	rr_ExpenseExampleNoRedemptionYear03	74
5 Years	rr_ExpenseExampleNoRedemptionYear05	130
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 293
2006	rr_AnnualReturn2006	8.24%	[1]
2007	rr_AnnualReturn2007	2.04%	[1]
2008	rr_AnnualReturn2008	(21.29%)	[1]
2009	rr_AnnualReturn2009	39.09%	[1]
2010	rr_AnnualReturn2010	12.40%	[1]
2011	rr_AnnualReturn2011	7.13%	[1]
2012	rr_AnnualReturn2012	14.36%	[1]
2013	rr_AnnualReturn2013	4.54%	[1]
2014	rr_AnnualReturn2014	4.58%	[1]
2015	rr_AnnualReturn2015	(1.39%)	[1]
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	2.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	14.43%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(13.94%)
1 Year	rr_AverageAnnualReturnYear01	(1.39%)
5 Years	rr_AverageAnnualReturnYear05	5.72%
10 Years	rr_AverageAnnualReturnYear10	6.02%
Investor Shares for Participants | Vanguard High-Yield Corporate Fund | Barclays U.S. Corporate High Yield Bond Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(4.47%)	[2]
5 Years	rr_AverageAnnualReturnYear05	5.04%	[2]
10 Years	rr_AverageAnnualReturnYear10	6.96%	[2]
Investor Shares for Participants | Vanguard High-Yield Corporate Fund | High-Yield Corporate Composite Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(2.53%)	[2]
5 Years	rr_AverageAnnualReturnYear05	5.23%	[2]
10 Years	rr_AverageAnnualReturnYear10	6.41%	[2]

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.30%.

[2] Comparative Indexes (reflect no deduction for fees or expenses)

XML

Admiral Shares for Participants | Vanguard High-Yield Corporate Fund

Fund Summary

Investment Objective

The Fund seeks to provide a high level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard High-Yield Corporate Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard High-Yield Corporate Fund Admiral Shares
Management Fees	0.12%
12b-1 Distribution Fee	none
Other Expenses	0.01%
Total Annual Fund Operating Expenses	0.13%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard High-Yield Corporate Fund | Admiral Shares | USD ($)	13	42	73	166

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 34% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor.

The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings.

• 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• 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 moderate for the Fund because it invests only a portion of its assets in callable bonds.

• Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 and loans and moderate for intermediate-term corporate bonds and loans.

• 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.

Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares.

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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares compare with those of a relevant market index and a composite index, which have investment characteristics similar to those of the Fund. 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 at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns — Vanguard High-Yield Corporate Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 14.47% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.92% (quarter ended December 31, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard High-Yield Corporate Fund		1 Year	5 Years	10 Years
Admiral Shares		(1.30%)	5.83%	6.14%
Barclays U.S. Corporate High Yield Bond Index	[1]	(4.47%)	5.04%	6.96%
High-Yield Corporate Composite Index	[1]	(2.53%)	5.23%	6.41%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.32%.

[1] Comparative Indexes (reflect no deduction for fees or expenses)

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard High-Yield Corporate Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 34% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	34.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 primarily in a diversified group of high-yielding, higher-risk corporate bonds—commonly known as “junk bonds”—with medium- and lower-range credit-quality ratings. The Fund invests at least 80% of its assets in corporate bonds that are rated below Baa by Moody’s Investors Service, Inc. (Moody’s); have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund may not invest more than 20% of its assets in any of the following, taken as a whole: bonds with credit ratings lower than B or the equivalent, convertible securities, preferred stocks, and fixed and floating rate loans of medium- to lower-range credit quality. The loans in which the Fund may invest will be rated Baa or below by Moody’s; have an equivalent rating by any other independent bond-rating agency; or, if unrated, are determined to be of comparable quality by the Fund’s advisor. The Fund’s high-yield bonds and loans mostly have short- and intermediate-term maturities.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Credit risk, which is the chance that a bond or loan 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 or loan to decline. Credit risk should be high for the Fund because it invests primarily in bonds and loans with medium- and lower-range credit-quality ratings. • 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 and moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • 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 moderate for the Fund because it invests only a portion of its assets in callable bonds. • Interest rate risk, which is the chance that bond or loan prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 and loans and moderate for intermediate-term corporate bonds and loans. • 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. Because of the speculative nature of junk bonds, you should carefully consider the risks associated with this Fund before you purchase shares. 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares compare with those of a relevant market index and a composite index, which have investment characteristics similar to those of the Fund. 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares compare with those of a relevant market index and a composite index, which have 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard High-Yield Corporate Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 14.47% (quarter ended June 30, 2009), and the lowest return for a quarter was –13.92% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard High-Yield Corporate 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
Management Fees	rr_ManagementFeesOverAssets	0.12%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.13%
1 Year	rr_ExpenseExampleYear01	$ 13
3 Years	rr_ExpenseExampleYear03	42
5 Years	rr_ExpenseExampleYear05	73
10 Years	rr_ExpenseExampleYear10	166
1 Year	rr_ExpenseExampleNoRedemptionYear01	13
3 Years	rr_ExpenseExampleNoRedemptionYear03	42
5 Years	rr_ExpenseExampleNoRedemptionYear05	73
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 166
2006	rr_AnnualReturn2006	8.38%	[1]
2007	rr_AnnualReturn2007	2.17%	[1]
2008	rr_AnnualReturn2008	(21.19%)	[1]
2009	rr_AnnualReturn2009	39.27%	[1]
2010	rr_AnnualReturn2010	12.53%	[1]
2011	rr_AnnualReturn2011	7.24%	[1]
2012	rr_AnnualReturn2012	14.47%	[1]
2013	rr_AnnualReturn2013	4.64%	[1]
2014	rr_AnnualReturn2014	4.69%	[1]
2015	rr_AnnualReturn2015	(1.30%)	[1]
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	2.32%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	14.47%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(13.92%)
1 Year	rr_AverageAnnualReturnYear01	(1.30%)
5 Years	rr_AverageAnnualReturnYear05	5.83%
10 Years	rr_AverageAnnualReturnYear10	6.14%
Admiral Shares for Participants | Vanguard High-Yield Corporate Fund | Barclays U.S. Corporate High Yield Bond Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(4.47%)	[2]
5 Years	rr_AverageAnnualReturnYear05	5.04%	[2]
10 Years	rr_AverageAnnualReturnYear10	6.96%	[2]
Admiral Shares for Participants | Vanguard High-Yield Corporate Fund | High-Yield Corporate Composite Index
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(2.53%)	[2]
5 Years	rr_AverageAnnualReturnYear05	5.23%	[2]
10 Years	rr_AverageAnnualReturnYear10	6.41%	[2]

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 2.32%.

[2] Comparative Indexes (reflect no deduction for fees or expenses)

XML

Investor Shares for Annuity | Vanguard GNMA Fund

Fund Summary

Investment Objective

The Fund seeks to provide a moderate level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Annuity Vanguard GNMA Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Annuity Vanguard GNMA Fund Investor Shares
Management Fees	0.18%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.21%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Annuity | Vanguard GNMA Fund | Investor Shares | USD ($)	22	68	118	268

This example does not include fees associated with the income annuity program through which you invest. Detailed information about the annuity program fees is presented in the “Fee Table” section of the accompanying prospectus of the insurance company for the annuity program through which Fund shares are offered.

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund.

• Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund.

• 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.

Annual Total Returns

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 Investor Shares compare with those of a relevant market index, which has investment characteristics similar to those of the Fund. The bar chart and table do not reflect additional fees and expenses that are deducted by the income annuity 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 at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns — Vanguard GNMA Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Annuity - Vanguard GNMA Fund	1 Year	5 Years	10 Years
Investor Shares	1.33%	3.10%	4.61%
Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)	1.39%	3.05%	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Annuity | Vanguard GNMA Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	706.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:
Expense Example Closing [Text Block]	rr_ExpenseExampleClosingTextBlock	This example does not include fees associated with the income annuity program through which you invest. Detailed information about the annuity program fees is presented in the “Fee Table” section of the accompanying prospectus of the insurance company for the annuity program through which Fund shares are offered.
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund. • Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund. • 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares compare with those of a relevant market index, which has investment characteristics similar to those of the Fund. The bar chart and table do not reflect additional fees and expenses that are deducted by the income annuity 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard GNMA Fund Investor Shares
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart and table do not reflect additional fees and expenses that are deducted by the income annuity 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.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Annuity | Vanguard GNMA 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
Management Fees	rr_ManagementFeesOverAssets	0.18%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
1 Year	rr_ExpenseExampleYear01	$ 22
3 Years	rr_ExpenseExampleYear03	68
5 Years	rr_ExpenseExampleYear05	118
10 Years	rr_ExpenseExampleYear10	268
1 Year	rr_ExpenseExampleNoRedemptionYear01	22
3 Years	rr_ExpenseExampleNoRedemptionYear03	68
5 Years	rr_ExpenseExampleNoRedemptionYear05	118
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 268
2006	rr_AnnualReturn2006	4.33%	[1]
2007	rr_AnnualReturn2007	7.01%	[1]
2008	rr_AnnualReturn2008	7.22%	[1]
2009	rr_AnnualReturn2009	5.29%	[1]
2010	rr_AnnualReturn2010	6.95%	[1]
2011	rr_AnnualReturn2011	7.69%	[1]
2012	rr_AnnualReturn2012	2.35%	[1]
2013	rr_AnnualReturn2013	(2.22%)	[1]
2014	rr_AnnualReturn2014	6.65%	[1]
2015	rr_AnnualReturn2015	1.33%	[1]
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	1.89%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.97%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(2.79%)
1 Year	rr_AverageAnnualReturnYear01	1.33%
5 Years	rr_AverageAnnualReturnYear05	3.10%
10 Years	rr_AverageAnnualReturnYear10	4.61%
Investor Shares for Annuity | Vanguard GNMA Fund | Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.39%
5 Years	rr_AverageAnnualReturnYear05	3.05%
10 Years	rr_AverageAnnualReturnYear10	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

Retail | Vanguard Short-Term Treasury Fund

Vanguard Short-Term Treasury Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Short-Term Treasury Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Short-Term Treasury Fund	Investor Shares	Admiral Shares
Management Fees	0.16%	0.08%
12b-1 Distribution Fee	none	none
Other Expenses	0.04%	0.02%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Short-Term Treasury Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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 211% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Short-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.38% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.14% (quarter ended June 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Short-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	0.45%	0.80%	2.61%
Investor Shares | Return After Taxes on Distributions	0.10%	0.49%	1.83%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.26%	0.50%	1.76%
Admiral Shares	0.55%	0.90%	2.73%
Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)	0.92%	1.24%	3.04%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.23%.

XML

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 Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Treasury 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 211% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	211.00%
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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. 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. • 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. 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 Treasury 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 3.38% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.14% (quarter ended June 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 Treasury 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	0.16%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.04%
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	3.77%	[2]
2007	rr_AnnualReturn2007	7.89%	[2]
2008	rr_AnnualReturn2008	6.68%	[2]
2009	rr_AnnualReturn2009	1.44%	[2]
2010	rr_AnnualReturn2010	2.64%	[2]
2011	rr_AnnualReturn2011	2.26%	[2]
2012	rr_AnnualReturn2012	0.69%	[2]
2013	rr_AnnualReturn2013	(0.10%)	[2]
2014	rr_AnnualReturn2014	0.71%	[2]
2015	rr_AnnualReturn2015	0.45%	[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	1.23%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.38%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(1.14%)
1 Year	rr_AverageAnnualReturnYear01	0.45%
5 Years	rr_AverageAnnualReturnYear05	0.80%
10 Years	rr_AverageAnnualReturnYear10	2.61%
Retail | Vanguard Short-Term Treasury 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	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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	0.55%
5 Years	rr_AverageAnnualReturnYear05	0.90%
10 Years	rr_AverageAnnualReturnYear10	2.73%
Retail | Vanguard Short-Term Treasury Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.10%
5 Years	rr_AverageAnnualReturnYear05	0.49%
10 Years	rr_AverageAnnualReturnYear10	1.83%
Retail | Vanguard Short-Term Treasury Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.26%
5 Years	rr_AverageAnnualReturnYear05	0.50%
10 Years	rr_AverageAnnualReturnYear10	1.76%
Retail | Vanguard Short-Term Treasury Fund | Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.92%
5 Years	rr_AverageAnnualReturnYear05	1.24%
10 Years	rr_AverageAnnualReturnYear10	3.04%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.23%.

XML

Retail | Vanguard Short-Term Federal Fund

Vanguard Short-Term Federal Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Short-Term Federal Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Short-Term Federal Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.08%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.02%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Short-Term Federal Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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 314% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Short-Term Federal Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.89% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.90% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Short-Term Federal Fund	1 Year	5 Years	10 Years
Investor Shares	0.73%	1.14%	3.03%
Investor Shares | Return After Taxes on Distributions	0.23%	0.70%	2.12%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.43%	0.72%	2.03%
Admiral Shares	0.83%	1.25%	3.13%
Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees, expenses, or taxes)	0.93%	1.23%	3.06%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.27%.

XML

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 Federal Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Federal 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 314% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	314.00%
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 at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. 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. • 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 Federal 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 3.89% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.90% (quarter ended June 30, 2013).
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 Federal 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	4.32%	[2]
2007	rr_AnnualReturn2007	7.43%	[2]
2008	rr_AnnualReturn2008	7.04%	[2]
2009	rr_AnnualReturn2009	2.79%	[2]
2010	rr_AnnualReturn2010	3.24%	[2]
2011	rr_AnnualReturn2011	2.76%	[2]
2012	rr_AnnualReturn2012	1.44%	[2]
2013	rr_AnnualReturn2013	(0.35%)	[2]
2014	rr_AnnualReturn2014	1.17%	[2]
2015	rr_AnnualReturn2015	0.73%	[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	1.27%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.89%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.90%)
1 Year	rr_AverageAnnualReturnYear01	0.73%
5 Years	rr_AverageAnnualReturnYear05	1.14%
10 Years	rr_AverageAnnualReturnYear10	3.03%
Retail | Vanguard Short-Term Federal 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	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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	0.83%
5 Years	rr_AverageAnnualReturnYear05	1.25%
10 Years	rr_AverageAnnualReturnYear10	3.13%
Retail | Vanguard Short-Term Federal Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.23%
5 Years	rr_AverageAnnualReturnYear05	0.70%
10 Years	rr_AverageAnnualReturnYear10	2.12%
Retail | Vanguard Short-Term Federal Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.43%
5 Years	rr_AverageAnnualReturnYear05	0.72%
10 Years	rr_AverageAnnualReturnYear10	2.03%
Retail | Vanguard Short-Term Federal Fund | Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.93%
5 Years	rr_AverageAnnualReturnYear05	1.23%
10 Years	rr_AverageAnnualReturnYear10	3.06%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.27%.

XML

Retail | Vanguard Short-Term Investment-Grade Fund

Vanguard Short-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Short-Term Investment-Grade Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Short-Term Investment-Grade Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.09%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.01%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Short-Term Investment-Grade Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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.

Principal Investment Strategies

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.

Principal Risks

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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Short-Term Investment-Grade Fund Investor Shares

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).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Short-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	1.03%	2.04%	3.46%
Investor Shares | Return After Taxes on Distributions	0.17%	1.11%	2.22%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.58%	1.21%	2.21%
Admiral Shares	1.13%	2.13%	3.56%
Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees, expenses, or taxes)	1.06%	2.55%	4.07%

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.

[1] /year

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

XML

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%.

XML

Retail | Vanguard Intermediate-Term Treasury Fund

Vanguard Intermediate-Term Treasury Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Intermediate-Term Treasury Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Intermediate-Term Treasury Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.09%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.01%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Intermediate-Term Treasury Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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 142% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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.

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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Intermediate-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 7.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.20% (quarter ended June 30, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Intermediate-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	1.50%	2.96%	4.61%
Investor Shares | Return After Taxes on Distributions	0.55%	1.97%	3.25%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.98%	2.01%	3.21%
Admiral Shares	1.61%	3.06%	4.74%
Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)	1.84%	3.92%	5.20%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.42%.

XML

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 Intermediate-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 142% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	142.00%
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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Intermediate-Term Treasury 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 7.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.20% (quarter ended June 30, 2009).
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 Intermediate-Term Treasury 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	3.14%	[2]
2007	rr_AnnualReturn2007	9.98%	[2]
2008	rr_AnnualReturn2008	13.32%	[2]
2009	rr_AnnualReturn2009	(1.69%)	[2]
2010	rr_AnnualReturn2010	7.35%	[2]
2011	rr_AnnualReturn2011	9.80%	[2]
2012	rr_AnnualReturn2012	2.67%	[2]
2013	rr_AnnualReturn2013	(3.09%)	[2]
2014	rr_AnnualReturn2014	4.32%	[2]
2015	rr_AnnualReturn2015	1.50%	[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	3.42%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.97%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.20%)
1 Year	rr_AverageAnnualReturnYear01	1.50%
5 Years	rr_AverageAnnualReturnYear05	2.96%
10 Years	rr_AverageAnnualReturnYear10	4.61%
Retail | Vanguard Intermediate-Term Treasury 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	1.61%
5 Years	rr_AverageAnnualReturnYear05	3.06%
10 Years	rr_AverageAnnualReturnYear10	4.74%
Retail | Vanguard Intermediate-Term Treasury Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.55%
5 Years	rr_AverageAnnualReturnYear05	1.97%
10 Years	rr_AverageAnnualReturnYear10	3.25%
Retail | Vanguard Intermediate-Term Treasury Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.98%
5 Years	rr_AverageAnnualReturnYear05	2.01%
10 Years	rr_AverageAnnualReturnYear10	3.21%
Retail | Vanguard Intermediate-Term Treasury Fund | Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.84%
5 Years	rr_AverageAnnualReturnYear05	3.92%
10 Years	rr_AverageAnnualReturnYear10	5.20%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.42%.

XML

Retail | Vanguard Intermediate-Term Investment-Grade Fund

Vanguard Intermediate-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Intermediate-Term Investment-Grade Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Intermediate-Term Investment-Grade Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.09%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.01%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Intermediate-Term Investment-Grade Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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 70% of the average value of its portfolio.

Principal Investment Strategies

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 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 moderate for intermediate-term corporate bonds.

• 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 moderate 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 moderate for intermediate-term bond funds.

• 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.

• 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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Intermediate-Term Investment-Grade Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 8.16% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.06% (quarter ended September 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Intermediate-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	1.53%	4.45%	5.34%
Investor Shares | Return After Taxes on Distributions	0.10%	2.72%	3.45%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.96%	2.87%	3.49%
Admiral Shares	1.63%	4.56%	5.45%
Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees, expenses, or taxes)	0.69%	4.98%	5.76%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.54%.

XML

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 Intermediate-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 70% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	70.00%
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 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 moderate for intermediate-term corporate bonds. • 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 moderate 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 moderate for intermediate-term bond funds. • 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. • 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	An investment in the Fund could lose money over short or even long periods.
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 Intermediate-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 8.16% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.06% (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 Intermediate-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	4.43%	[2]
2007	rr_AnnualReturn2007	6.14%	[2]
2008	rr_AnnualReturn2008	(6.16%)	[2]
2009	rr_AnnualReturn2009	17.73%	[2]
2010	rr_AnnualReturn2010	10.47%	[2]
2011	rr_AnnualReturn2011	7.52%	[2]
2012	rr_AnnualReturn2012	9.14%	[2]
2013	rr_AnnualReturn2013	(1.37%)	[2]
2014	rr_AnnualReturn2014	5.81%	[2]
2015	rr_AnnualReturn2015	1.53%	[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	3.54%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.16%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(6.06%)
1 Year	rr_AverageAnnualReturnYear01	1.53%
5 Years	rr_AverageAnnualReturnYear05	4.45%
10 Years	rr_AverageAnnualReturnYear10	5.34%
Retail | Vanguard Intermediate-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	1.63%
5 Years	rr_AverageAnnualReturnYear05	4.56%
10 Years	rr_AverageAnnualReturnYear10	5.45%
Retail | Vanguard Intermediate-Term Investment-Grade Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.10%
5 Years	rr_AverageAnnualReturnYear05	2.72%
10 Years	rr_AverageAnnualReturnYear10	3.45%
Retail | Vanguard Intermediate-Term Investment-Grade Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.96%
5 Years	rr_AverageAnnualReturnYear05	2.87%
10 Years	rr_AverageAnnualReturnYear10	3.49%
Retail | Vanguard Intermediate-Term Investment-Grade Fund | Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.69%
5 Years	rr_AverageAnnualReturnYear05	4.98%
10 Years	rr_AverageAnnualReturnYear10	5.76%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.54%.

XML

Retail | Vanguard GNMA Fund

Vanguard GNMA Fund

Investment Objective

The Fund seeks to provide a moderate level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard GNMA Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard GNMA Fund	Investor Shares	Admiral Shares
Management Fees	0.18%	0.09%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.02%
Total Annual Fund Operating Expenses	0.21%	0.11%

Examples

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:

Expense Example - Retail - Vanguard GNMA Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	22	68	118	268
Admiral Shares	11	35	62	141

Portfolio Turnover

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 706% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund.

• Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund.

• 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.

Annual Total Returns

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.

Annual Total Returns — Vanguard GNMA Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard GNMA Fund	1 Year	5 Years	10 Years
Investor Shares	1.33%	3.10%	4.61%
Investor Shares | Return After Taxes on Distributions	0.15%	1.86%	3.07%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	0.80%	1.90%	3.00%
Admiral Shares	1.43%	3.20%	4.72%
Barclays U.S. GNMA Bond Index (reflects no deduction for fees, expenses, or taxes)	1.39%	3.05%	4.66%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

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 GNMA Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard GNMA Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate level of current income.
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 706% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	706.00%
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 at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund. • Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund. • 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	An investment in the Fund could lose money over short or even long periods.
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 GNMA 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 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).
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 GNMA 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	0.18%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
1 Year	rr_ExpenseExampleYear01	$ 22
3 Years	rr_ExpenseExampleYear03	68
5 Years	rr_ExpenseExampleYear05	118
10 Years	rr_ExpenseExampleYear10	268
1 Year	rr_ExpenseExampleNoRedemptionYear01	22
3 Years	rr_ExpenseExampleNoRedemptionYear03	68
5 Years	rr_ExpenseExampleNoRedemptionYear05	118
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 268
2006	rr_AnnualReturn2006	4.33%	[2]
2007	rr_AnnualReturn2007	7.01%	[2]
2008	rr_AnnualReturn2008	7.22%	[2]
2009	rr_AnnualReturn2009	5.29%	[2]
2010	rr_AnnualReturn2010	6.95%	[2]
2011	rr_AnnualReturn2011	7.69%	[2]
2012	rr_AnnualReturn2012	2.35%	[2]
2013	rr_AnnualReturn2013	(2.22%)	[2]
2014	rr_AnnualReturn2014	6.65%	[2]
2015	rr_AnnualReturn2015	1.33%	[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	1.89%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.97%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(2.79%)
1 Year	rr_AverageAnnualReturnYear01	1.33%
5 Years	rr_AverageAnnualReturnYear05	3.10%
10 Years	rr_AverageAnnualReturnYear10	4.61%
Retail | Vanguard GNMA 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	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.11%
1 Year	rr_ExpenseExampleYear01	$ 11
3 Years	rr_ExpenseExampleYear03	35
5 Years	rr_ExpenseExampleYear05	62
10 Years	rr_ExpenseExampleYear10	141
1 Year	rr_ExpenseExampleNoRedemptionYear01	11
3 Years	rr_ExpenseExampleNoRedemptionYear03	35
5 Years	rr_ExpenseExampleNoRedemptionYear05	62
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 141
1 Year	rr_AverageAnnualReturnYear01	1.43%
5 Years	rr_AverageAnnualReturnYear05	3.20%
10 Years	rr_AverageAnnualReturnYear10	4.72%
Retail | Vanguard GNMA Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.15%
5 Years	rr_AverageAnnualReturnYear05	1.86%
10 Years	rr_AverageAnnualReturnYear10	3.07%
Retail | Vanguard GNMA Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.80%
5 Years	rr_AverageAnnualReturnYear05	1.90%
10 Years	rr_AverageAnnualReturnYear10	3.00%
Retail | Vanguard GNMA Fund | Barclays U.S. GNMA Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.39%
5 Years	rr_AverageAnnualReturnYear05	3.05%
10 Years	rr_AverageAnnualReturnYear10	4.66%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

Retail | Vanguard Long-Term Treasury Fund

Vanguard Long-Term Treasury Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Long-Term Treasury Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Long-Term Treasury Fund	Investor Shares	Admiral Shares
Management Fees	0.17%	0.08%
12b-1 Distribution Fee	none	none
Other Expenses	0.03%	0.02%
Total Annual Fund Operating Expenses	0.20%	0.10%

Examples

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:

Expense Example - Retail - Vanguard Long-Term Treasury Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	20	64	113	255
Admiral Shares	10	32	56	128

Portfolio Turnover

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 117% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Long-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 24.73% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.70% (quarter ended June 30, 2015).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Long-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	(1.54%)	7.49%	6.47%
Investor Shares | Return After Taxes on Distributions	(3.32%)	5.63%	4.56%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	(0.41%)	5.27%	4.46%
Admiral Shares	(1.44%)	7.60%	6.60%
Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)	(1.21%)	7.74%	6.73%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.30%.

XML

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 Long-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 117% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	117.00%
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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Long-Term Treasury 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 24.73% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.70% (quarter ended June 30, 2015).
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 Long-Term Treasury 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	1.74%	[2]
2007	rr_AnnualReturn2007	9.24%	[2]
2008	rr_AnnualReturn2008	22.52%	[2]
2009	rr_AnnualReturn2009	(12.05%)	[2]
2010	rr_AnnualReturn2010	8.93%	[2]
2011	rr_AnnualReturn2011	29.28%	[2]
2012	rr_AnnualReturn2012	3.47%	[2]
2013	rr_AnnualReturn2013	(13.03%)	[2]
2014	rr_AnnualReturn2014	25.28%	[2]
2015	rr_AnnualReturn2015	(1.54%)	[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	8.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	24.73%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.70%)
1 Year	rr_AverageAnnualReturnYear01	(1.54%)
5 Years	rr_AverageAnnualReturnYear05	7.49%
10 Years	rr_AverageAnnualReturnYear10	6.47%
Retail | Vanguard Long-Term Treasury 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	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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	(1.44%)
5 Years	rr_AverageAnnualReturnYear05	7.60%
10 Years	rr_AverageAnnualReturnYear10	6.60%
Retail | Vanguard Long-Term Treasury Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(3.32%)
5 Years	rr_AverageAnnualReturnYear05	5.63%
10 Years	rr_AverageAnnualReturnYear10	4.56%
Retail | Vanguard Long-Term Treasury Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(0.41%)
5 Years	rr_AverageAnnualReturnYear05	5.27%
10 Years	rr_AverageAnnualReturnYear10	4.46%
Retail | Vanguard Long-Term Treasury Fund | Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.21%)
5 Years	rr_AverageAnnualReturnYear05	7.74%
10 Years	rr_AverageAnnualReturnYear10	6.73%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.30%.

XML

Retail | Vanguard Long-Term Investment-Grade Fund

Vanguard Long-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

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

(Fees paid directly from your investment)

Shareholder Fees - Retail - Vanguard Long-Term Investment-Grade Fund - USD ($)		Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases		none	none
Purchase Fee		none	none
Sales Charge (Load) Imposed on Reinvested Dividends		none	none
Redemption Fee		none	none
Account Service Fee (for certain fund account balances below $10,000)	[1]	$ 20	$ 20

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Retail - Vanguard Long-Term Investment-Grade Fund	Investor Shares	Admiral Shares
Management Fees	0.19%	0.10%
12b-1 Distribution Fee	none	none
Other Expenses	0.02%	0.02%
Total Annual Fund Operating Expenses	0.21%	0.12%

Examples

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:

Expense Example - Retail - Vanguard Long-Term Investment-Grade Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Investor Shares	22	68	118	268
Admiral Shares	12	39	68	154

Portfolio Turnover

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 35% of the average value of its portfolio.

Principal Investment Strategies

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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• 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 high for long-term corporate bonds.

• 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called.

• 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 high for long-term bond funds.

• 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.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

Annual Total Returns

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.

Annual Total Returns — Vanguard Long-Term Investment-Grade Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 11.33% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.28% (quarter ended March 31, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Retail - Vanguard Long-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	(2.21%)	7.32%	6.46%
Investor Shares | Return After Taxes on Distributions	(4.42%)	5.04%	4.26%
Investor Shares | Return After Taxes on Distributions and Sale of Fund Shares	(0.93%)	4.84%	4.17%
Admiral Shares	(2.11%)	7.42%	6.58%
Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees, expenses, or taxes)	(1.95%)	7.11%	6.05%

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.

[1] /year

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.77%.

XML

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 Long-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 35% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	35.00%
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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • 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 high for long-term corporate bonds. • 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called. • 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 high for long-term bond funds. • 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. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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	An investment in the Fund could lose money over short or even long periods.
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 Long-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 11.33% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.28% (quarter ended March 31, 2009).
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 Long-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	0.19%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
1 Year	rr_ExpenseExampleYear01	$ 22
3 Years	rr_ExpenseExampleYear03	68
5 Years	rr_ExpenseExampleYear05	118
10 Years	rr_ExpenseExampleYear10	268
1 Year	rr_ExpenseExampleNoRedemptionYear01	22
3 Years	rr_ExpenseExampleNoRedemptionYear03	68
5 Years	rr_ExpenseExampleNoRedemptionYear05	118
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 268
2006	rr_AnnualReturn2006	2.86%	[2]
2007	rr_AnnualReturn2007	3.75%	[2]
2008	rr_AnnualReturn2008	2.29%	[2]
2009	rr_AnnualReturn2009	8.75%	[2]
2010	rr_AnnualReturn2010	10.71%	[2]
2011	rr_AnnualReturn2011	17.18%	[2]
2012	rr_AnnualReturn2012	11.66%	[2]
2013	rr_AnnualReturn2013	(5.87%)	[2]
2014	rr_AnnualReturn2014	18.17%	[2]
2015	rr_AnnualReturn2015	(2.21%)	[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	6.77%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	11.33%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.28%)
1 Year	rr_AverageAnnualReturnYear01	(2.21%)
5 Years	rr_AverageAnnualReturnYear05	7.32%
10 Years	rr_AverageAnnualReturnYear10	6.46%
Retail | Vanguard Long-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	0.10%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.12%
1 Year	rr_ExpenseExampleYear01	$ 12
3 Years	rr_ExpenseExampleYear03	39
5 Years	rr_ExpenseExampleYear05	68
10 Years	rr_ExpenseExampleYear10	154
1 Year	rr_ExpenseExampleNoRedemptionYear01	12
3 Years	rr_ExpenseExampleNoRedemptionYear03	39
5 Years	rr_ExpenseExampleNoRedemptionYear05	68
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 154
1 Year	rr_AverageAnnualReturnYear01	(2.11%)
5 Years	rr_AverageAnnualReturnYear05	7.42%
10 Years	rr_AverageAnnualReturnYear10	6.58%
Retail | Vanguard Long-Term Investment-Grade Fund | Return After Taxes on Distributions | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(4.42%)
5 Years	rr_AverageAnnualReturnYear05	5.04%
10 Years	rr_AverageAnnualReturnYear10	4.26%
Retail | Vanguard Long-Term Investment-Grade Fund | Return After Taxes on Distributions and Sale of Fund Shares | Investor Shares
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(0.93%)
5 Years	rr_AverageAnnualReturnYear05	4.84%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Retail | Vanguard Long-Term Investment-Grade Fund | Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.95%)
5 Years	rr_AverageAnnualReturnYear05	7.11%
10 Years	rr_AverageAnnualReturnYear10	6.05%

[1] /year

[2] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.77%.

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Investor Shares for Participants | Vanguard Short-Term Treasury Fund

Vanguard Short-Term Treasury Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Short-Term Treasury Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Short-Term Treasury Fund Investor Shares
Management Fees	0.16%
12b-1 Distribution Fee	none
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Short-Term Treasury Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 211% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Short-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.38% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.14% (quarter ended June 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Short-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	0.45%	0.80%	2.61%
Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees or expenses)	0.92%	1.24%	3.04%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.23%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Short-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Treasury 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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 211% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	211.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. 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. • 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. 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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Short-Term Treasury 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 3.38% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.14% (quarter ended June 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Short-Term Treasury 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
Management Fees	rr_ManagementFeesOverAssets	0.16%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.04%
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	3.77%	[1]
2007	rr_AnnualReturn2007	7.89%	[1]
2008	rr_AnnualReturn2008	6.68%	[1]
2009	rr_AnnualReturn2009	1.44%	[1]
2010	rr_AnnualReturn2010	2.64%	[1]
2011	rr_AnnualReturn2011	2.26%	[1]
2012	rr_AnnualReturn2012	0.69%	[1]
2013	rr_AnnualReturn2013	(0.10%)	[1]
2014	rr_AnnualReturn2014	0.71%	[1]
2015	rr_AnnualReturn2015	0.45%	[1]
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	1.23%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.38%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(1.14%)
1 Year	rr_AverageAnnualReturnYear01	0.45%
5 Years	rr_AverageAnnualReturnYear05	0.80%
10 Years	rr_AverageAnnualReturnYear10	2.61%
Investor Shares for Participants | Vanguard Short-Term Treasury Fund | Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.92%
5 Years	rr_AverageAnnualReturnYear05	1.24%
10 Years	rr_AverageAnnualReturnYear10	3.04%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.23%.

XML

Investor Shares for Participants | Vanguard Short-Term Federal Fund

Vanguard Short-Term Federal Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Short-Term Federal Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Short-Term Federal Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Short-Term Federal Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 314% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Short-Term Federal Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.89% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.90% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Short-Term Federal Fund	1 Year	5 Years	10 Years
Investor Shares	0.73%	1.14%	3.03%
Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees or expenses)	0.93%	1.23%	3.06%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.27%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Short-Term Federal Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Federal 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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 314% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	314.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. 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. • 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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Short-Term Federal 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 3.89% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.90% (quarter ended June 30, 2013).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Short-Term Federal 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
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	4.32%	[1]
2007	rr_AnnualReturn2007	7.43%	[1]
2008	rr_AnnualReturn2008	7.04%	[1]
2009	rr_AnnualReturn2009	2.79%	[1]
2010	rr_AnnualReturn2010	3.24%	[1]
2011	rr_AnnualReturn2011	2.76%	[1]
2012	rr_AnnualReturn2012	1.44%	[1]
2013	rr_AnnualReturn2013	(0.35%)	[1]
2014	rr_AnnualReturn2014	1.17%	[1]
2015	rr_AnnualReturn2015	0.73%	[1]
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	1.27%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.89%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.90%)
1 Year	rr_AverageAnnualReturnYear01	0.73%
5 Years	rr_AverageAnnualReturnYear05	1.14%
10 Years	rr_AverageAnnualReturnYear10	3.03%
Investor Shares for Participants | Vanguard Short-Term Federal Fund | Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.93%
5 Years	rr_AverageAnnualReturnYear05	1.23%
10 Years	rr_AverageAnnualReturnYear10	3.06%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.27%.

XML

Investor Shares for Participants | Vanguard Short-Term Investment-Grade Fund

Vanguard Short-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Short-Term Investment-Grade Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Short-Term Investment-Grade Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Short-Term Investment-Grade Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, 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.

Principal Investment Strategies

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.

Principal Risks

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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Short-Term Investment-Grade Fund Investor Shares

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).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Short-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	1.03%	2.04%	3.46%
Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees or expenses)	1.06%	2.55%	4.07%

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

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | 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 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 example, 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	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 Investor Shares 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 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 Investor Shares 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 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
Investor Shares for Participants | 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
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%	[1]
2007	rr_AnnualReturn2007	5.86%	[1]
2008	rr_AnnualReturn2008	(4.74%)	[1]
2009	rr_AnnualReturn2009	14.03%	[1]
2010	rr_AnnualReturn2010	5.21%	[1]
2011	rr_AnnualReturn2011	1.93%	[1]
2012	rr_AnnualReturn2012	4.52%	[1]
2013	rr_AnnualReturn2013	0.97%	[1]
2014	rr_AnnualReturn2014	1.76%	[1]
2015	rr_AnnualReturn2015	1.03%	[1]
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%
Investor Shares for Participants | Vanguard Short-Term Investment-Grade Fund | Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.06%
5 Years	rr_AverageAnnualReturnYear05	2.55%
10 Years	rr_AverageAnnualReturnYear10	4.07%

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

XML

Investor Shares for Participants | Vanguard Intermediate-Term Treasury Fund

Vanguard Intermediate-Term Treasury Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Intermediate-Term Treasury Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Intermediate-Term Treasury Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Intermediate-Term Treasury Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 142% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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.

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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Intermediate-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 7.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.20% (quarter ended June 30, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Intermediate-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	1.50%	2.96%	4.61%
Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees or expenses)	1.84%	3.92%	5.20%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.42%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Intermediate-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 142% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	142.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Intermediate-Term Treasury 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 7.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.20% (quarter ended June 30, 2009).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Intermediate-Term Treasury 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
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	3.14%	[1]
2007	rr_AnnualReturn2007	9.98%	[1]
2008	rr_AnnualReturn2008	13.32%	[1]
2009	rr_AnnualReturn2009	(1.69%)	[1]
2010	rr_AnnualReturn2010	7.35%	[1]
2011	rr_AnnualReturn2011	9.80%	[1]
2012	rr_AnnualReturn2012	2.67%	[1]
2013	rr_AnnualReturn2013	(3.09%)	[1]
2014	rr_AnnualReturn2014	4.32%	[1]
2015	rr_AnnualReturn2015	1.50%	[1]
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	3.42%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.97%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.20%)
1 Year	rr_AverageAnnualReturnYear01	1.50%
5 Years	rr_AverageAnnualReturnYear05	2.96%
10 Years	rr_AverageAnnualReturnYear10	4.61%
Investor Shares for Participants | Vanguard Intermediate-Term Treasury Fund | Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.84%
5 Years	rr_AverageAnnualReturnYear05	3.92%
10 Years	rr_AverageAnnualReturnYear10	5.20%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.42%.

XML

Investor Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund

Vanguard Intermediate-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Intermediate-Term Investment-Grade Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses	Investor Shares for Participants Vanguard Intermediate-Term Investment-Grade Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 70% of the average value of its portfolio.

Principal Investment Strategies

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 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 moderate for intermediate-term corporate bonds.

• 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 moderate 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 moderate for intermediate-term bond funds.

• 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.

• 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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Intermediate-Term Investment-Grade Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 8.16% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.06% (quarter ended September 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Intermediate-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	1.53%	4.45%	5.34%
Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees or expenses)	0.69%	4.98%	5.76%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.54%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 70% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	70.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 moderate for intermediate-term corporate bonds. • 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 moderate 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 moderate for intermediate-term bond funds. • 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. • 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Intermediate-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 8.16% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.06% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Intermediate-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
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	4.43%	[1]
2007	rr_AnnualReturn2007	6.14%	[1]
2008	rr_AnnualReturn2008	(6.16%)	[1]
2009	rr_AnnualReturn2009	17.73%	[1]
2010	rr_AnnualReturn2010	10.47%	[1]
2011	rr_AnnualReturn2011	7.52%	[1]
2012	rr_AnnualReturn2012	9.14%	[1]
2013	rr_AnnualReturn2013	(1.37%)	[1]
2014	rr_AnnualReturn2014	5.81%	[1]
2015	rr_AnnualReturn2015	1.53%	[1]
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	3.54%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.16%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(6.06%)
1 Year	rr_AverageAnnualReturnYear01	1.53%
5 Years	rr_AverageAnnualReturnYear05	4.45%
10 Years	rr_AverageAnnualReturnYear10	5.34%
Investor Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund | Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.69%
5 Years	rr_AverageAnnualReturnYear05	4.98%
10 Years	rr_AverageAnnualReturnYear10	5.76%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.54%.

XML

Investor Shares for Participants | Vanguard GNMA Fund

Vanguard GNMA Fund

Investment Objective

The Fund seeks to provide a moderate level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard GNMA Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard GNMA Fund Investor Shares
Management Fees	0.18%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.21%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard GNMA Fund | Investor Shares | USD ($)	22	68	118	268

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund.

• Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund.

• 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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard GNMA Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard GNMA Fund	1 Year	5 Years	10 Years
Investor Shares	1.33%	3.10%	4.61%
Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)	1.39%	3.05%	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard GNMA Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard GNMA Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	706.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund. • Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund. • 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard GNMA 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 3.97% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.79% (quarter ended June 30, 2013).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard GNMA 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
Management Fees	rr_ManagementFeesOverAssets	0.18%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.03%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
1 Year	rr_ExpenseExampleYear01	$ 22
3 Years	rr_ExpenseExampleYear03	68
5 Years	rr_ExpenseExampleYear05	118
10 Years	rr_ExpenseExampleYear10	268
1 Year	rr_ExpenseExampleNoRedemptionYear01	22
3 Years	rr_ExpenseExampleNoRedemptionYear03	68
5 Years	rr_ExpenseExampleNoRedemptionYear05	118
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 268
2006	rr_AnnualReturn2006	4.33%	[1]
2007	rr_AnnualReturn2007	7.01%	[1]
2008	rr_AnnualReturn2008	7.22%	[1]
2009	rr_AnnualReturn2009	5.29%	[1]
2010	rr_AnnualReturn2010	6.95%	[1]
2011	rr_AnnualReturn2011	7.69%	[1]
2012	rr_AnnualReturn2012	2.35%	[1]
2013	rr_AnnualReturn2013	(2.22%)	[1]
2014	rr_AnnualReturn2014	6.65%	[1]
2015	rr_AnnualReturn2015	1.33%	[1]
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	1.89%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.97%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(2.79%)
1 Year	rr_AverageAnnualReturnYear01	1.33%
5 Years	rr_AverageAnnualReturnYear05	3.10%
10 Years	rr_AverageAnnualReturnYear10	4.61%
Investor Shares for Participants | Vanguard GNMA Fund | Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.39%
5 Years	rr_AverageAnnualReturnYear05	3.05%
10 Years	rr_AverageAnnualReturnYear10	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.89%.

XML

Investor Shares for Participants | Vanguard Long-Term Treasury Fund

Vanguard Long-Term Treasury Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Long-Term Treasury Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Long-Term Treasury Fund Investor Shares
Management Fees	0.17%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Long-Term Treasury Fund | Investor Shares | USD ($)	20	64	113	255

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 117% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Long-Term Treasury Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 24.73% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.70% (quarter ended June 30, 2015).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Long-Term Treasury Fund	1 Year	5 Years	10 Years
Investor Shares	(1.54%)	7.49%	6.47%
Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees or expenses)	(1.21%)	7.74%	6.73%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.30%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Long-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 117% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	117.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Long-Term Treasury 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 24.73% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.70% (quarter ended June 30, 2015).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Long-Term Treasury 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
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	1.74%	[1]
2007	rr_AnnualReturn2007	9.24%	[1]
2008	rr_AnnualReturn2008	22.52%	[1]
2009	rr_AnnualReturn2009	(12.05%)	[1]
2010	rr_AnnualReturn2010	8.93%	[1]
2011	rr_AnnualReturn2011	29.28%	[1]
2012	rr_AnnualReturn2012	3.47%	[1]
2013	rr_AnnualReturn2013	(13.03%)	[1]
2014	rr_AnnualReturn2014	25.28%	[1]
2015	rr_AnnualReturn2015	(1.54%)	[1]
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	8.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	24.73%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.70%)
1 Year	rr_AverageAnnualReturnYear01	(1.54%)
5 Years	rr_AverageAnnualReturnYear05	7.49%
10 Years	rr_AverageAnnualReturnYear10	6.47%
Investor Shares for Participants | Vanguard Long-Term Treasury Fund | Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.21%)
5 Years	rr_AverageAnnualReturnYear05	7.74%
10 Years	rr_AverageAnnualReturnYear10	6.73%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.30%.

XML

Investor Shares for Participants | Vanguard Long-Term Investment-Grade Fund

Vanguard Long-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Investor Shares for Participants Vanguard Long-Term Investment-Grade Fund Investor Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Investor Shares for Participants Vanguard Long-Term Investment-Grade Fund Investor Shares
Management Fees	0.19%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.21%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Investor Shares for Participants | Vanguard Long-Term Investment-Grade Fund | Investor Shares | USD ($)	22	68	118	268

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 35% of the average value of its portfolio.

Principal Investment Strategies

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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• 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 high for long-term corporate bonds.

• 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called.

• 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 high for long-term bond funds.

• 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.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

Annual Total Returns

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 Investor Shares 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 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.

Annual Total Returns — Vanguard Long-Term Investment-Grade Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 11.33% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.28% (quarter ended March 31, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Investor Shares for Participants - Vanguard Long-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Investor Shares	(2.21%)	7.32%	6.46%
Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees or expenses)	(1.95%)	7.11%	6.05%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.77%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Investor Shares for Participants | Vanguard Long-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 35% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	35.00%
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 Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • 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 high for long-term corporate bonds. • 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called. • 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 high for long-term bond funds. • 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. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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	An investment in the Fund could lose money over short or even long periods.
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 Investor Shares 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 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 Investor Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Long-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 11.33% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.28% (quarter ended March 31, 2009).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Investor Shares for Participants | Vanguard Long-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
Management Fees	rr_ManagementFeesOverAssets	0.19%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
1 Year	rr_ExpenseExampleYear01	$ 22
3 Years	rr_ExpenseExampleYear03	68
5 Years	rr_ExpenseExampleYear05	118
10 Years	rr_ExpenseExampleYear10	268
1 Year	rr_ExpenseExampleNoRedemptionYear01	22
3 Years	rr_ExpenseExampleNoRedemptionYear03	68
5 Years	rr_ExpenseExampleNoRedemptionYear05	118
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 268
2006	rr_AnnualReturn2006	2.86%	[1]
2007	rr_AnnualReturn2007	3.75%	[1]
2008	rr_AnnualReturn2008	2.29%	[1]
2009	rr_AnnualReturn2009	8.75%	[1]
2010	rr_AnnualReturn2010	10.71%	[1]
2011	rr_AnnualReturn2011	17.18%	[1]
2012	rr_AnnualReturn2012	11.66%	[1]
2013	rr_AnnualReturn2013	(5.87%)	[1]
2014	rr_AnnualReturn2014	18.17%	[1]
2015	rr_AnnualReturn2015	(2.21%)	[1]
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	6.77%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	11.33%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.28%)
1 Year	rr_AverageAnnualReturnYear01	(2.21%)
5 Years	rr_AverageAnnualReturnYear05	7.32%
10 Years	rr_AverageAnnualReturnYear10	6.46%
Investor Shares for Participants | Vanguard Long-Term Investment-Grade Fund | Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.95%)
5 Years	rr_AverageAnnualReturnYear05	7.11%
10 Years	rr_AverageAnnualReturnYear10	6.05%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.77%.

XML

Admiral Shares for Participants | Vanguard Short-Term Treasury Fund

Vanguard Short-Term Treasury Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Short-Term Treasury Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Short-Term Treasury Fund Admiral Shares
Management Fees	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Short-Term Treasury Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 211% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Short-Term Treasury Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.41% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.12% (quarter ended June 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Short-Term Treasury Fund	1 Year	5 Years	10 Years
Admiral Shares	0.55%	0.90%	2.73%
Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees or expenses)	0.92%	1.24%	3.04%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.26%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Short-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Treasury 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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 211% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	211.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. 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. • 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. 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Short-Term Treasury Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 3.41% (quarter ended March 31, 2008), and the lowest return for a quarter was –1.12% (quarter ended June 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Short-Term Treasury 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
Management Fees	rr_ManagementFeesOverAssets	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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
2006	rr_AnnualReturn2006	3.93%	[1]
2007	rr_AnnualReturn2007	8.02%	[1]
2008	rr_AnnualReturn2008	6.79%	[1]
2009	rr_AnnualReturn2009	1.54%	[1]
2010	rr_AnnualReturn2010	2.76%	[1]
2011	rr_AnnualReturn2011	2.36%	[1]
2012	rr_AnnualReturn2012	0.79%	[1]
2013	rr_AnnualReturn2013	none	[1]
2014	rr_AnnualReturn2014	0.82%	[1]
2015	rr_AnnualReturn2015	0.55%	[1]
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	1.26%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.41%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(1.12%)
1 Year	rr_AverageAnnualReturnYear01	0.55%
5 Years	rr_AverageAnnualReturnYear05	0.90%
10 Years	rr_AverageAnnualReturnYear10	2.73%
Admiral Shares for Participants | Vanguard Short-Term Treasury Fund | Barclays U.S. 1-5 Year Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.92%
5 Years	rr_AverageAnnualReturnYear05	1.24%
10 Years	rr_AverageAnnualReturnYear10	3.04%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.26%.

XML

Admiral Shares for Participants | Vanguard Short-Term Federal Fund

Vanguard Short-Term Federal Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Short-Term Federal Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Short-Term Federal Fund Admiral Shares
Management Fees	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Short-Term Federal Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 314% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. The Fund is expected to maintain a dollar-weighted average maturity of 1 to 4 years.

Principal Risks

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.

• 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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Short-Term Federal Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 3.91% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.87% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Short-Term Federal Fund	1 Year	5 Years	10 Years
Admiral Shares	0.83%	1.25%	3.13%
Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees or expenses)	0.93%	1.23%	3.06%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.30%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Short-Term Federal Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Short-Term Federal 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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 314% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	314.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in short-term bonds issued or guaranteed by the U.S. government and its agencies and instrumentalities, many of which are not backed by the full faith and credit of the U.S. government. 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. • 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Short-Term Federal Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 3.91% (quarter ended December 31, 2008), and the lowest return for a quarter was –0.87% (quarter ended June 30, 2013).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Short-Term Federal 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
Management Fees	rr_ManagementFeesOverAssets	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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
2006	rr_AnnualReturn2006	4.42%	[1]
2007	rr_AnnualReturn2007	7.53%	[1]
2008	rr_AnnualReturn2008	7.15%	[1]
2009	rr_AnnualReturn2009	2.89%	[1]
2010	rr_AnnualReturn2010	3.36%	[1]
2011	rr_AnnualReturn2011	2.86%	[1]
2012	rr_AnnualReturn2012	1.54%	[1]
2013	rr_AnnualReturn2013	(0.25%)	[1]
2014	rr_AnnualReturn2014	1.27%	[1]
2015	rr_AnnualReturn2015	0.83%	[1]
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	1.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.91%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.87%)
1 Year	rr_AverageAnnualReturnYear01	0.83%
5 Years	rr_AverageAnnualReturnYear05	1.25%
10 Years	rr_AverageAnnualReturnYear10	3.13%
Admiral Shares for Participants | Vanguard Short-Term Federal Fund | Barclays U.S. 1-5 Year Government Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.93%
5 Years	rr_AverageAnnualReturnYear05	1.23%
10 Years	rr_AverageAnnualReturnYear10	3.06%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.30%.

XML

Admiral Shares for Participants | Vanguard Short-Term Investment-Grade Fund

Vanguard Short-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide current income while maintaining limited price volatility.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Short-Term Investment-Grade Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Short-Term Investment-Grade Fund Admiral Shares
Management Fees	0.09%
12b-1 Distribution Fee	none
Other Expenses	0.01%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Short-Term Investment-Grade Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, 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.

Principal Investment Strategies

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.

Principal Risks

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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Short-Term Investment-Grade Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 6.05% (quarter ended June 30, 2009), and the lowest return for a quarter was –3.39% (quarter ended September 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Short-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Admiral Shares	1.13%	2.13%	3.56%
Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees or expenses)	1.06%	2.55%	4.07%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.76%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | 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 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 example, 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	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 6.05% (quarter ended June 30, 2009), and the lowest return for a quarter was –3.39% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | 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
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
2006	rr_AnnualReturn2006	5.11%	[1]
2007	rr_AnnualReturn2007	5.98%	[1]
2008	rr_AnnualReturn2008	(4.65%)	[1]
2009	rr_AnnualReturn2009	14.17%	[1]
2010	rr_AnnualReturn2010	5.33%	[1]
2011	rr_AnnualReturn2011	2.02%	[1]
2012	rr_AnnualReturn2012	4.63%	[1]
2013	rr_AnnualReturn2013	1.07%	[1]
2014	rr_AnnualReturn2014	1.86%	[1]
2015	rr_AnnualReturn2015	1.13%	[1]
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	1.76%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.05%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.39%)
1 Year	rr_AverageAnnualReturnYear01	1.13%
5 Years	rr_AverageAnnualReturnYear05	2.13%
10 Years	rr_AverageAnnualReturnYear10	3.56%
Admiral Shares for Participants | Vanguard Short-Term Investment-Grade Fund | Barclays U.S. 1-5 Year Credit Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.06%
5 Years	rr_AverageAnnualReturnYear05	2.55%
10 Years	rr_AverageAnnualReturnYear10	4.07%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.76%.

XML

Admiral Shares for Participants | Vanguard Intermediate-Term Treasury Fund

Vanguard Intermediate-Term Treasury Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Intermediate-Term Treasury Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Intermediate-Term Treasury Fund Admiral Shares
Management Fees	0.09%
12b-1 Distribution Fee	none
Other Expenses	0.01%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Intermediate-Term Treasury Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 142% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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.

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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Intermediate-Term Treasury Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 8.00% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.17% (quarter ended June 30, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Intermediate-Term Treasury Fund	1 Year	5 Years	10 Years
Admiral Shares	1.61%	3.06%	4.74%
Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees or expenses)	1.84%	3.92%	5.20%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.45%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Intermediate-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 142% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	142.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Intermediate-Term Treasury Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 8.00% (quarter ended December 31, 2008), and the lowest return for a quarter was –3.17% (quarter ended June 30, 2009).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Intermediate-Term Treasury 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
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
2006	rr_AnnualReturn2006	3.30%	[1]
2007	rr_AnnualReturn2007	10.15%	[1]
2008	rr_AnnualReturn2008	13.49%	[1]
2009	rr_AnnualReturn2009	(1.56%)	[1]
2010	rr_AnnualReturn2010	7.48%	[1]
2011	rr_AnnualReturn2011	9.91%	[1]
2012	rr_AnnualReturn2012	2.78%	[1]
2013	rr_AnnualReturn2013	(2.99%)	[1]
2014	rr_AnnualReturn2014	4.42%	[1]
2015	rr_AnnualReturn2015	1.61%	[1]
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	3.45%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.00%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.17%)
1 Year	rr_AverageAnnualReturnYear01	1.61%
5 Years	rr_AverageAnnualReturnYear05	3.06%
10 Years	rr_AverageAnnualReturnYear10	4.74%
Admiral Shares for Participants | Vanguard Intermediate-Term Treasury Fund | Barclays U.S. 5-10 Year Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.84%
5 Years	rr_AverageAnnualReturnYear05	3.92%
10 Years	rr_AverageAnnualReturnYear10	5.20%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.45%.

XML

Admiral Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund

Vanguard Intermediate-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a moderate and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Intermediate-Term Investment-Grade Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses	Admiral Shares for Participants Vanguard Intermediate-Term Investment-Grade Fund Admiral Shares
Management Fees	0.09%
12b-1 Distribution Fee	none
Other Expenses	0.01%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 70% of the average value of its portfolio.

Principal Investment Strategies

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 5 to 10 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds.

• 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 moderate for intermediate-term corporate bonds.

• 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 moderate 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 moderate for intermediate-term bond funds.

• 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.

• 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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Intermediate-Term Investment-Grade Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 8.19% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.04% (quarter ended September 30, 2008).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Intermediate-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Admiral Shares	1.63%	4.56%	5.45%
Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees or expenses)	0.69%	4.98%	5.76%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.57%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Intermediate-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 70% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	70.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 5 to 10 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. 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 moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be moderate for the Fund because it invests primarily in short- and intermediate-term bonds, whose prices are less sensitive to interest rate changes than are the prices of long-term bonds. • 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 moderate for intermediate-term corporate bonds. • 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 moderate 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 moderate for intermediate-term bond funds. • 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. • 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Intermediate-Term Investment-Grade Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 8.19% (quarter ended June 30, 2009), and the lowest return for a quarter was –6.04% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Intermediate-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
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
2006	rr_AnnualReturn2006	4.55%	[1]
2007	rr_AnnualReturn2007	6.26%	[1]
2008	rr_AnnualReturn2008	(6.06%)	[1]
2009	rr_AnnualReturn2009	17.88%	[1]
2010	rr_AnnualReturn2010	10.60%	[1]
2011	rr_AnnualReturn2011	7.63%	[1]
2012	rr_AnnualReturn2012	9.25%	[1]
2013	rr_AnnualReturn2013	(1.27%)	[1]
2014	rr_AnnualReturn2014	5.91%	[1]
2015	rr_AnnualReturn2015	1.63%	[1]
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	3.57%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.19%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(6.04%)
1 Year	rr_AverageAnnualReturnYear01	1.63%
5 Years	rr_AverageAnnualReturnYear05	4.56%
10 Years	rr_AverageAnnualReturnYear10	5.45%
Admiral Shares for Participants | Vanguard Intermediate-Term Investment-Grade Fund | Barclays U.S. 5-10 Year Credit Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.69%
5 Years	rr_AverageAnnualReturnYear05	4.98%
10 Years	rr_AverageAnnualReturnYear10	5.76%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 3.57%.

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Admiral Shares for Participants | Vanguard GNMA Fund

Vanguard GNMA Fund

Investment Objective

The Fund seeks to provide a moderate level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard GNMA Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard GNMA Fund Admiral Shares
Management Fees	0.09%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.11%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard GNMA Fund | Admiral Shares | USD ($)	11	35	62	141

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund.

• Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund.

• 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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard GNMA Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 4.00% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.77% (quarter ended June 30, 2013).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard GNMA Fund	1 Year	5 Years	10 Years
Admiral Shares	1.43%	3.20%	4.72%
Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)	1.39%	3.05%	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.91%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard GNMA Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard GNMA Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a moderate level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 706% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	706.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 at least 80% of its assets in Government National Mortgage Association (GNMA) pass-through certificates, which are fixed income securities representing part ownership in a pool of mortgage loans supported by the full faith and credit of the U.S. government. The balance of the Fund’s assets may be invested in other types of securities such as U.S. Treasury or other U.S. government agency securities, including pass-through certificates, as well as in repurchase agreements collateralized by such securities. Securities issued by most U.S. government agencies, other than the U.S. Treasury and GNMA, are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. The Fund’s dollar-weighted average maturity depends on homeowner prepayments of the underlying mortgages. Although the Fund does not observe specific maturity guidelines, the Fund’s dollar-weighted average maturity will normally fall within an intermediate-term range (3 to 10 years).
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Prepayment risk, which is the chance that during periods of falling interest rates, homeowners will refinance their mortgages before their maturity dates, resulting in prepayment of mortgage-backed securities held by the Fund. The Fund would then lose any price appreciation above the mortgage’s principal and would be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Such prepayments and subsequent reinvestments would also increase the Fund’s portfolio turnover rate. Prepayment risk is high for the Fund. • Extension risk, which is the chance that during periods of rising interest rates, homeowners will prepay their mortgages at slower rates. This will lengthen the duration or average life of mortgage-backed securities held by the Fund and delay the Fund’s ability to reinvest proceeds at higher interest rates. Extension risk is high for the Fund. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk is generally moderate for intermediate-term bond funds, so investors should expect the Fund’s monthly income to fluctuate accordingly. • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. In addition, when interest rates decline, GNMA prices typically do not rise as much as the prices of comparable bonds. This is because the market tends to discount GNMA prices for prepayment risk when interest rates decline. Interest rate risk should be moderate for the Fund. • 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard GNMA Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 4.00% (quarter ended December 31, 2008), and the lowest return for a quarter was –2.77% (quarter ended June 30, 2013).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard GNMA 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
Management Fees	rr_ManagementFeesOverAssets	0.09%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.11%
1 Year	rr_ExpenseExampleYear01	$ 11
3 Years	rr_ExpenseExampleYear03	35
5 Years	rr_ExpenseExampleYear05	62
10 Years	rr_ExpenseExampleYear10	141
1 Year	rr_ExpenseExampleNoRedemptionYear01	11
3 Years	rr_ExpenseExampleNoRedemptionYear03	35
5 Years	rr_ExpenseExampleNoRedemptionYear05	62
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 141
2006	rr_AnnualReturn2006	4.43%	[1]
2007	rr_AnnualReturn2007	7.11%	[1]
2008	rr_AnnualReturn2008	7.33%	[1]
2009	rr_AnnualReturn2009	5.40%	[1]
2010	rr_AnnualReturn2010	7.08%	[1]
2011	rr_AnnualReturn2011	7.80%	[1]
2012	rr_AnnualReturn2012	2.45%	[1]
2013	rr_AnnualReturn2013	(2.13%)	[1]
2014	rr_AnnualReturn2014	6.76%	[1]
2015	rr_AnnualReturn2015	1.43%	[1]
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	1.91%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	4.00%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(2.77%)
1 Year	rr_AverageAnnualReturnYear01	1.43%
5 Years	rr_AverageAnnualReturnYear05	3.20%
10 Years	rr_AverageAnnualReturnYear10	4.72%
Admiral Shares for Participants | Vanguard GNMA Fund | Barclays U.S. GNMA Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.39%
5 Years	rr_AverageAnnualReturnYear05	3.05%
10 Years	rr_AverageAnnualReturnYear10	4.66%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 1.91%.

XML

Admiral Shares for Participants | Vanguard Long-Term Treasury Fund

Vanguard Long-Term Treasury Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Long-Term Treasury Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Long-Term Treasury Fund Admiral Shares
Management Fees	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Long-Term Treasury Fund | Admiral Shares | USD ($)	10	32	56	128

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 117% of the average value of its portfolio.

Principal Investment Strategies

The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund's share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund's performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Long-Term Treasury Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 24.76% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.67% (quarter ended June 30, 2015).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Long-Term Treasury Fund	1 Year	5 Years	10 Years
Admiral Shares	(1.44%)	7.60%	6.60%
Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees or expenses)	(1.21%)	7.74%	6.73%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.33%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Long-Term Treasury Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Treasury Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 117% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	117.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:
1 Year	rr_ExpenseExampleNoRedemptionYear01	$ 10
3 Years	rr_ExpenseExampleNoRedemptionYear03	32
5 Years	rr_ExpenseExampleNoRedemptionYear05	56
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 128
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests at least 80% of its assets in U.S. Treasury securities, which include bills, bonds, and notes issued by the U.S. Treasury. The Fund is expected to maintain a dollar-weighted average maturity of 15 to 30 years.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund's share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund's performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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. 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Long-Term Treasury Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 24.76% (quarter ended September 30, 2011), and the lowest return for a quarter was –8.67% (quarter ended June 30, 2015).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Long-Term Treasury 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
Management Fees	rr_ManagementFeesOverAssets	0.08%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
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
2006	rr_AnnualReturn2006	1.91%	[1]
2007	rr_AnnualReturn2007	9.42%	[1]
2008	rr_AnnualReturn2008	22.69%	[1]
2009	rr_AnnualReturn2009	(11.93%)	[1]
2010	rr_AnnualReturn2010	9.06%	[1]
2011	rr_AnnualReturn2011	29.41%	[1]
2012	rr_AnnualReturn2012	3.57%	[1]
2013	rr_AnnualReturn2013	(12.94%)	[1]
2014	rr_AnnualReturn2014	25.40%	[1]
2015	rr_AnnualReturn2015	(1.44%)	[1]
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	8.33%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	24.76%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.67%)
1 Year	rr_AverageAnnualReturnYear01	(1.44%)
5 Years	rr_AverageAnnualReturnYear05	7.60%
10 Years	rr_AverageAnnualReturnYear10	6.60%
Admiral Shares for Participants | Vanguard Long-Term Treasury Fund | Barclays U.S. Long Treasury Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.21%)
5 Years	rr_AverageAnnualReturnYear05	7.74%
10 Years	rr_AverageAnnualReturnYear10	6.73%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 8.33%.

XML

Admiral Shares for Participants | Vanguard Long-Term Investment-Grade Fund

Vanguard Long-Term Investment-Grade Fund

Investment Objective

The Fund seeks to provide a high and sustainable level of current income.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral Shares of the Fund.

Shareholder Fees

(Fees paid directly from your investment)

Shareholder Fees	Admiral Shares for Participants Vanguard Long-Term Investment-Grade Fund Admiral Shares
Sales Charge (Load) Imposed on Purchases	none
Purchase Fee	none
Sales Charge (Load) Imposed on Reinvested Dividends	none
Redemption Fee	none

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Admiral Shares for Participants Vanguard Long-Term Investment-Grade Fund Admiral Shares
Management Fees	0.10%
12b-1 Distribution Fee	none
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.12%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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:

Expense Example	1 Year	3 Years	5 Years	10 Years
Admiral Shares for Participants | Vanguard Long-Term Investment-Grade Fund | Admiral Shares | USD ($)	12	39	68	154

Portfolio Turnover

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 35% of the average value of its portfolio.

Principal Investment Strategies

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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.

Principal Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds.

• 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 high for long-term corporate bonds.

• 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called.

• 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 high for long-term bond funds.

• 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.

• Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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.

Annual Total Returns

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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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.

Annual Total Returns — Vanguard Long-Term Investment-Grade Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 11.37% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.25% (quarter ended March 31, 2009).

Average Annual Total Returns for Periods Ended December 31, 2015

Average Annual Total Returns - Admiral Shares for Participants - Vanguard Long-Term Investment-Grade Fund	1 Year	5 Years	10 Years
Admiral Shares	(2.11%)	7.42%	6.58%
Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees or expenses)	(1.95%)	7.11%	6.05%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.80%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Admiral Shares for Participants | Vanguard Long-Term Investment-Grade Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Vanguard Long-Term Investment-Grade Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to provide a high and sustainable level of current income.
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 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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 35% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	35.00%
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 Fund’s Admiral Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. This example assumes 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 intermediate- and long-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’s dollar-weighted average maturity is expected to fall within a range that is five years shorter than or five years longer than that of its benchmark index, which had a dollar-weighted average maturity of 23.2 years as of January 31, 2016. The Fund uses multiple investment advisors.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range. The Fund is subject to the following risks, which could affect the Fund’s performance: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. Interest rate risk should be high for the Fund because it invests primarily in long-term bonds, whose prices are more sensitive to interest rate changes than are the prices of shorter-term bonds. • 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 high for long-term corporate bonds. • 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 moderate for the Fund. To minimize the impact of call risk, the advisors generally seek to purchase bonds that have reasonable protection from being called. • 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 high for long-term bond funds. • 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. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. Income risk should be low for the Fund because it invests primarily in long-term 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	An investment in the Fund could lose money over short or even long periods.
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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 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 Admiral Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Admiral Shares 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 does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns — Vanguard Long-Term Investment-Grade Fund Admiral Shares
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the periods shown in the bar chart, the highest return for a calendar quarter was 11.37% (quarter ended September 30, 2009), and the lowest return for a quarter was –8.25% (quarter ended March 31, 2009).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns for Periods Ended December 31, 2015
Admiral Shares for Participants | Vanguard Long-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
Management Fees	rr_ManagementFeesOverAssets	0.10%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.12%
1 Year	rr_ExpenseExampleYear01	$ 12
3 Years	rr_ExpenseExampleYear03	39
5 Years	rr_ExpenseExampleYear05	68
10 Years	rr_ExpenseExampleYear10	154
1 Year	rr_ExpenseExampleNoRedemptionYear01	12
3 Years	rr_ExpenseExampleNoRedemptionYear03	39
5 Years	rr_ExpenseExampleNoRedemptionYear05	68
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 154
2006	rr_AnnualReturn2006	2.99%	[1]
2007	rr_AnnualReturn2007	3.86%	[1]
2008	rr_AnnualReturn2008	2.40%	[1]
2009	rr_AnnualReturn2009	8.89%	[1]
2010	rr_AnnualReturn2010	10.85%	[1]
2011	rr_AnnualReturn2011	17.30%	[1]
2012	rr_AnnualReturn2012	11.77%	[1]
2013	rr_AnnualReturn2013	(5.77%)	[1]
2014	rr_AnnualReturn2014	18.29%	[1]
2015	rr_AnnualReturn2015	(2.11%)	[1]
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	6.80%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	11.37%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.25%)
1 Year	rr_AverageAnnualReturnYear01	(2.11%)
5 Years	rr_AverageAnnualReturnYear05	7.42%
10 Years	rr_AverageAnnualReturnYear10	6.58%
Admiral Shares for Participants | Vanguard Long-Term Investment-Grade Fund | Barclays U.S. Long Credit A or Better Bond Index (reflects no deduction for fees or expenses)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(1.95%)
5 Years	rr_AverageAnnualReturnYear05	7.11%
10 Years	rr_AverageAnnualReturnYear10	6.05%

[1] The year-to-date return as of the most recent calendar quarter, which ended on March 31, 2016, was 6.80%.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD FIXED INCOME SECURITIES FUNDS
Prospectus Date	rr_ProspectusDate	May 26, 2016
Document Creation Date	dei_DocumentCreationDate	May 26, 2016