Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD MUNICIPAL BOND FUNDS
Prospectus Date	rr_ProspectusDate	Feb. 26, 2016
ETF | Vanguard Tax-Exempt Bond Index Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	ETF Summary
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks to track the performance of a benchmark index that measures the investment-grade segment of the U.S. municipal bond market.
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 ETF 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 August 21, 2015, to October 31, 2015, the Fund’s portfolio turnover rate was 1% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	1.00%
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	This example does not include the brokerage commissions that you may pay to buy and sell ETF Shares of the Fund.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The expense information shown in the table reflects the estimated amounts for the current fiscal year.
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 ETF Shares with the cost of investing in other 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 the brokerage commissions that you may pay to buy and sell ETF Shares of the Fund.
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund employs an indexing investment approach designed to track the Standard & Poor’s National AMT-Free Municipal Bond Index, which measures the performance of the investment-grade segment of the U.S. municipal bond market. This Index includes municipal bonds from issuers that are primarily state or local governments or agencies whose interest is exempt from U.S. federal income taxes and the federal alternative minimum tax (AMT). To be eligible for inclusion in the Index, each bond must have a rating of at least investment-grade, as determined by a nationally recognized statistical rating organization (e.g., at least BBB– by Fitch Ratings, Inc.); be denominated in U.S. dollars; and have a minimum par amount of $25 million. In addition, to be included in the Index, each bond must have a minimum term to maturity or call date greater than one calendar month. The Fund invests by sampling the Index, meaning that it holds a range of securities that, in the aggregate, approximates the full Index in terms of key risk factors and other characteristics. All of the Fund’s investments will be selected through the sampling process, and at least 80% of the Fund’s assets will be invested in securities held in the Index. Under normal circumstances, at least 80% of the Fund’s assets will be invested in securities whose income will be exempt from federal income taxes and the federal alternative minimum tax.
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: • Interest rate risk, which is the chance that bond prices will decline because of rising interest rates. • Income risk, which is the chance that the Fund’s income will decline because of falling interest rates. • 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. • 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. • 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. In general, credit risk should be low for the Fund because it invests primarily in bonds that are considered to be of high quality. • Index sampling risk, which is the chance that the securities selected for the Fund, in the aggregate, will not provide investment performance matching that of the Fund’s target index. Index sampling risk for the Fund should be low to moderate. • 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. • Tax risk, which is the chance that all or a portion of the tax-exempt income from municipal bonds held by the Fund will be declared taxable, possibly with retroactive effect, because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state or local tax authorities, or noncompliant conduct of a bond issuer. Because ETF Shares are traded on an exchange, they are subject to additional risks: • The Fund’s ETF Shares are listed for trading on NYSE Arca and are bought and sold on the secondary market at market prices. Although it is expected that the market price of an ETF Share typically will approximate its net asset value (NAV), there may be times when the market price and the NAV differ significantly. Thus, you may pay more or less than NAV when you buy ETF Shares on the secondary market, and you may receive more or less than NAV when you sell those shares. • Although the Fund’s ETF Shares are listed for trading on NYSE Arca, it is possible that an active trading market may not be maintained. • Trading of the Fund’s ETF Shares may be halted by the activation of individual or marketwide trading halts (which halt trading for a specific period of time when the price of a particular security or overall market prices decline by a specified percentage). Trading of the Fund’s ETF Shares may also be halted if (1) the shares are delisted from NYSE Arca without first being listed on another exchange or (2) NYSE Arca officials determine that such action is appropriate in the interest of a fair and orderly market or for the protection of investors. 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
ETF | Vanguard Tax-Exempt Bond Index Fund | ETF Shares
Risk/Return:	rr_RiskReturnAbstract
Transaction Fee on Purchases and Sales	municipal_TransactionFeeOnPurchasesandSales	none	[1]
Transaction Fee on Reinvested Dividends	municipal_TransactionFeeOnReinvestedDividends	none	[1]
Transaction Fee on Conversion to ETF Shares	municipal_TransactionFeeOnConversionToETFShares	none	[1]
Management Fees	rr_ManagementFeesOverAssets	0.02%
12b-1 Distribution Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.12%	[2]
1 Year	rr_ExpenseExampleYear01	$ 12
3 Years	rr_ExpenseExampleYear03	39
1 Year	rr_ExpenseExampleNoRedemptionYear01	12
3 Years	rr_ExpenseExampleNoRedemptionYear03	$ 39

[1] None through Vanguard (Broker fees vary)

[2] The expense information shown in the table reflects the estimated amounts for the current fiscal year.