Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY MUNICIPAL TRUST II
12.31 Fidelity Pennsylvania Municipal Funds Combo PRO-11 | Fidelity Pennsylvania Municipal Money Market Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary Fund:Fidelity® Pennsylvania Municipal Money Market Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks as high a level of current income, exempt from federal income tax and Pennsylvania personal income tax, as is consistent with preservation of capital.
Expense [Heading]	rr_ExpenseHeading	Fee Table
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees
(fees paid directly from your investment)	rr_ShareholderFeeOther	none
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Operating Expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Normally investing in municipal money market securities. Normally investing at least 80% of assets in municipal securities whose interest is exempt from federal and Pennsylvania personal income taxes. Potentially investing up to 20% of assets in municipal securities whose interest is subject to Pennsylvania personal income tax. Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects. Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, liquidity, and diversification of investments.
Risk [Heading]	rr_RiskHeading	Principal Investment Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Municipal Market Volatility. The municipal market is volatile and can be significantly affected by adverse tax, legislative, or political changes and the financial condition of the issuers of municipal securities. Interest Rate Changes. Interest rate increases can cause the price of a money market security to decrease. Income Risk. A low or negative interest rate environment can adversely affect the fund’s yield. Foreign Exposure. Entities providing credit support or a maturity-shortening structure that are located in foreign countries can be affected by adverse political, regulatory, market, or economic developments in those countries. Geographic Concentration. Unfavorable political or economic conditions within Pennsylvania can affect the credit quality of issuers located in that state. Issuer-Specific Changes. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease. You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The fund may impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if the fund's liquidity falls below required minimums because of market conditions or other factors. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Fidelity Investments and its affiliates, the fund’s sponsor, have no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money by investing in the fund.
Risk Money Market Fund May Impose Fees or Suspend Sales [Text]	rr_RiskMoneyMarketFundMayImposeFeesOrSuspendSales	The fund may impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if the fund's liquidity falls below required minimums because of market conditions or other factors.
Risk Money Market Fund Sponsor May Not Provide Support [Text]	rr_RiskMoneyMarketFundSponsorMayNotProvideSupport	Fidelity Investments and its affiliates, the fund’s sponsor, have no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
Risk Money Market Fund May Not Preserve Dollar [Text]	rr_RiskMoneyMarketFundMayNotPreserveDollar	Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year. Past performance is not an indication of future performance. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information illustrates the changes in the performance of the fund's shares from year to year.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.fidelity.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	Past performance is not an indication of future performance.
Bar Chart [Heading]	rr_BarChartHeading	Year-by-Year Returns
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Returns
12.31 Fidelity Pennsylvania Municipal Funds Combo PRO-11 | Fidelity Pennsylvania Municipal Money Market Fund | Fidelity Pennsylvania Municipal Money Market Fund
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	none
Total annual operating expenses	rr_ExpensesOverAssets	0.50%	[1]
1 year	rr_ExpenseExampleYear01	$ 51
3 years	rr_ExpenseExampleYear03	160
5 years	rr_ExpenseExampleYear05	280
10 years	rr_ExpenseExampleYear10	$ 628
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.01%
2014	rr_AnnualReturn2014	0.01%
2015	rr_AnnualReturn2015	0.01%
2016	rr_AnnualReturn2016	0.09%
2017	rr_AnnualReturn2017	0.40%
2018	rr_AnnualReturn2018	0.97%
2019	rr_AnnualReturn2019	1.06%
2020	rr_AnnualReturn2020	0.37%
2021	rr_AnnualReturn2021	0.08%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Highest Quarter Return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2019
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.31%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Lowest Quarter Return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
12.31 Fidelity Pennsylvania Municipal Funds Combo PRO-11 | Fidelity Pennsylvania Municipal Money Market Fund | Return Before Taxes | Fidelity Pennsylvania Municipal Money Market Fund
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Fidelity® Pennsylvania Municipal Money Market Fund
Past 1 year	rr_AverageAnnualReturnYear01	0.08%
Past 5 years	rr_AverageAnnualReturnYear05	0.57%
Past 10 years	rr_AverageAnnualReturnYear10	0.30%

[1] ^(a)In order to avoid a negative yield, Fidelity Management & Research Company LLC (FMR) may reimburse expenses or waive fees of Fidelity^® Pennsylvania Municipal Money Market Fund. Any such waivers or expense reimbursement would be voluntary and could be discontinued at any time. There is no guarantee that Fidelity^® Pennsylvania Municipal Money Market Fund will be able to avoid a negative yield.