XML 13 R29.htm IDEA: XBRL DOCUMENT v2.4.0.6
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Jan. 31, 2012
Registrant Name dei_EntityRegistrantName FIDELITY MASSACHUSETTS MUNICIPAL TRUST
Central Index Key dei_EntityCentralIndexKey 0000357057
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 29, 2012
Document Effective Date dei_DocumentEffectiveDate Mar. 31, 2012
Prospectus Date rr_ProspectusDate Mar. 31, 2012
Fidelity Massachusetts Municipal Income Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund:
Fidelity® Massachusetts Municipal Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks a high level of current income, exempt from federal income tax and Massachusetts personal income tax.
Fee Table fmmt357057_FundFeesAndExpensesAbstract  
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, hold, or sell shares of the fund.
Shareholder Fees rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual fund operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
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 mutual 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:
Portfolio Turnover fmmt357057_PortfolioTurnoverAltAbstract  
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 higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 11% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 11.00%
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in investment-grade municipal securities whose interest is exempt from federal and Massachusetts personal income taxes.
  • Managing the fund to have similar overall interest rate risk to an index designed to represent Fidelity Management & Research Company (FMR)'s view of how the fund's competitive universe will perform over time.
  • Allocating assets across different market sectors and maturities.
  • Potentially investing more than 25% of total assets in municipal securities that finance similar types of projects.
  • Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select 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 debt security to decrease.
  • Geographic Concentration. Unfavorable political or economic conditions within Massachusetts can affect the credit quality of issuers located in that state.
  • Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. 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 security to decrease.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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. Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will fluctuate. You could lose money by investing in the fund.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.
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.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money by investing in the fund.
Performance fmmt357057_FundPastPerformanceAbstract  
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 and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return 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 and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return6.55%September 30, 2009
Lowest Quarter Return-4.08%December 31, 2010
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances.
For the periods ended
December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.
Fidelity Massachusetts Municipal Income Fund | Class: Fidelity Massachusetts Municipal Income Fund
  
Shareholder Fees rr_ShareholderFeesAbstract  
Redemption fee on shares held less than 30 days (as a % of amount redeemed) rr_RedemptionFeeOverRedemption 0.50%
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.37%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.09%
Total annual operating expenses rr_ExpensesOverAssets 0.46%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 47
3 years rr_ExpenseExampleYear03 148
5 years rr_ExpenseExampleYear05 258
10 years rr_ExpenseExampleYear10 579
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 9.70%
2003 rr_AnnualReturn2003 5.31%
2004 rr_AnnualReturn2004 4.54%
2005 rr_AnnualReturn2005 3.62%
2006 rr_AnnualReturn2006 4.70%
2007 rr_AnnualReturn2007 3.29%
2008 rr_AnnualReturn2008 (3.57%)
2009 rr_AnnualReturn2009 12.69%
2010 rr_AnnualReturn2010 2.36%
2011 rr_AnnualReturn2011 10.37%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.55%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.08%)
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2010
Fidelity Massachusetts Municipal Income Fund | Return Before Taxes | Class: Fidelity Massachusetts Municipal Income Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Massachusetts Municipal Income Fund
Label rr_AverageAnnualReturnLabel Return Before Taxes
Past 1 year rr_AverageAnnualReturnYear01 10.37%
Past 5 years rr_AverageAnnualReturnYear05 4.86%
Past 10 years rr_AverageAnnualReturnYear10 5.21%
Fidelity Massachusetts Municipal Income Fund | Return After Taxes on Distributions | Class: Fidelity Massachusetts Municipal Income Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Massachusetts Municipal Income Fund
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
Past 1 year rr_AverageAnnualReturnYear01 10.31%
Past 5 years rr_AverageAnnualReturnYear05 4.83%
Past 10 years rr_AverageAnnualReturnYear10 5.11%
Fidelity Massachusetts Municipal Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Massachusetts Municipal Income Fund
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Column rr_AverageAnnualReturnColumnName Fidelity Massachusetts Municipal Income Fund
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year rr_AverageAnnualReturnYear01 8.19%
Past 5 years rr_AverageAnnualReturnYear05 4.72%
Past 10 years rr_AverageAnnualReturnYear10 5.04%
Fidelity Massachusetts Municipal Income Fund | Barclays Capital® Municipal Bond Index (reflects no deduction for fees, expenses, or taxes)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays Capital® Municipal Bond Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Past 1 year rr_AverageAnnualReturnYear01 10.70%
Past 5 years rr_AverageAnnualReturnYear05 5.22%
Past 10 years rr_AverageAnnualReturnYear10 5.38%
Fidelity Massachusetts Municipal Income Fund | Barclays Capital Massachusetts 3+ Year Enhanced Municipal Bond Index (reflects no deduction for fees, expenses, or taxes)
  
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays Capital Massachusetts 3+ Year Enhanced Municipal Bond Index
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Past 1 year rr_AverageAnnualReturnYear01 11.91%
Past 5 years rr_AverageAnnualReturnYear05 5.88%
Past 10 years rr_AverageAnnualReturnYear10 5.82%
Fidelity Massachusetts Municipal Money Market Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund:
Fidelity® Massachusetts 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 Massachusetts personal income tax, as is consistent with preservation of capital.
Fee Table fmmt357057_FundFeesAndExpensesAbstract  
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 rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual fund operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
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 mutual 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:
Portfolio Turnover fmmt357057_PortfolioTurnoverAltAbstract  
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 Massachusetts personal income taxes.
  • Potentially investing up to 20% of assets in municipal securities whose interest is subject to Massachusetts 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, 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.
  • 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 Massachusetts 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.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
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.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fmmt357057_FundPastPerformanceAbstract  
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 updated return 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 Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.82%September 30, 2007
Lowest Quarter Return0.00%March 31, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
For the periods ended
December 31, 2011
Fidelity Massachusetts Municipal Money Market Fund | Class: Fidelity Massachusetts Municipal Money Market Fund
  
Shareholder Fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.37%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.13%
Total annual operating expenses rr_ExpensesOverAssets 0.50%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 51
3 years rr_ExpenseExampleYear03 160
5 years rr_ExpenseExampleYear05 280
10 years rr_ExpenseExampleYear10 628
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 1.05%
2003 rr_AnnualReturn2003 0.60%
2004 rr_AnnualReturn2004 0.77%
2005 rr_AnnualReturn2005 1.96%
2006 rr_AnnualReturn2006 2.98%
2007 rr_AnnualReturn2007 3.20%
2008 rr_AnnualReturn2008 1.67%
2009 rr_AnnualReturn2009 0.07%
2010 rr_AnnualReturn2010 0.02%
2011 rr_AnnualReturn2011 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.82%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2007
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Fidelity Massachusetts Municipal Money Market Fund
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 0.99%
Past 10 years rr_AverageAnnualReturnYear10 1.23%
Retail | Fidelity Massachusetts AMT Tax-Free Money Market Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Fidelity® Massachusetts AMT Tax-Free Money Market Fund/Fidelity Massachusetts AMT Tax-Free Money Market Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks as high a level of income, exempt from federal and Massachusetts personal income tax, as is consistent with the preservation of capital and liquidity.
Fee Table fmmt357057_FundFeesAndExpensesAbstract  
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 rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Expense Example rr_ExpenseExampleAbstract  
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 mutual 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:

Portfolio Turnover fmmt357057_PortfolioTurnoverAltAbstract  
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 Massachusetts personal income taxes.
  • Potentially investing up to 20% of assets in municipal securities whose interest is subject to Massachusetts personal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum 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, 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.
  • 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 Massachusetts 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.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.

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.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fmmt357057_FundPastPerformanceAbstract  
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 updated return 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 Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.87%June 30, 2007
Lowest Quarter Return0.00%June 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
For the periods ended
December 31, 2011
Retail | Fidelity Massachusetts AMT Tax-Free Money Market Fund | Class: Fidelity Massachusetts AMT Tax-Free Money Market Fund
  
Shareholder Fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.20%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.10%
Total annual operating expenses rr_ExpensesOverAssets 0.30%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 31
3 years rr_ExpenseExampleYear03 97
5 years rr_ExpenseExampleYear05 169
10 years rr_ExpenseExampleYear10 381
Annual Total Returns rr_BarChartTableAbstract  
2002 rr_AnnualReturn2002 1.15%
2003 rr_AnnualReturn2003 0.71%
2004 rr_AnnualReturn2004 0.88%
2005 rr_AnnualReturn2005 2.07%
2006 rr_AnnualReturn2006 3.10%
2007 rr_AnnualReturn2007 3.39%
2008 rr_AnnualReturn2008 1.85%
2009 rr_AnnualReturn2009 0.18%
2010 rr_AnnualReturn2010 0.01%
2011 rr_AnnualReturn2011 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.87%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2007
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Fidelity Massachusetts AMT Tax-Free Money Market Fund
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Past 5 years rr_AverageAnnualReturnYear05 1.08%
Past 10 years rr_AverageAnnualReturnYear10 1.33%
Inst | Fidelity Massachusetts AMT Tax-Free Money Market Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Fidelity® Massachusetts AMT Tax-Free Money Market Fund/Institutional
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks as high a level of income, exempt from federal and Massachusetts personal income tax, as is consistent with the preservation of capital and liquidity.
Fee Table fmmt357057_FundFeesAndExpensesAbstract  
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 rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination at least one year from the effective date of the prospectus
Expense Example rr_ExpenseExampleAbstract  
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 mutual 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:
Portfolio Turnover fmmt357057_PortfolioTurnoverAltAbstract  
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 Massachusetts personal income taxes.
  • Potentially investing up to 20% of assets in municipal securities whose interest is subject to Massachusetts personal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum 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, 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.
  • 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 Massachusetts 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.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
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.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fmmt357057_FundPastPerformanceAbstract  
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 or www.advisor.fidelity.com for updated return 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 Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.fidelity.com or www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.61%March 31, 2008
Lowest Quarter Return0.00%September 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
For the periods ended
December 31, 2011
Inst | Fidelity Massachusetts AMT Tax-Free Money Market Fund | Institutional Class
  
Shareholder Fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.20%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.05%
Total annual operating expenses rr_ExpensesOverAssets 0.25%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.05% [1]
Total annual operating expenses after fee waiver and/or expense reimbursement rr_NetExpensesOverAssets 0.20%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 20
3 years rr_ExpenseExampleYear03 64
5 years rr_ExpenseExampleYear05 113
10 years rr_ExpenseExampleYear10 255
Annual Total Returns rr_BarChartTableAbstract  
2008 rr_AnnualReturn2008 1.95%
2009 rr_AnnualReturn2009 0.28%
2010 rr_AnnualReturn2010 0.09%
2011 rr_AnnualReturn2011 0.03%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.61%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2008
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Institutional Class
Past 1 year rr_AverageAnnualReturnYear01 0.03%
Life of class rr_AverageAnnualReturnSinceInception 1.02% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 18, 2007
Service | Fidelity Massachusetts AMT Tax-Free Money Market Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
Fund Summary
Fund/Class:
Fidelity® Massachusetts AMT Tax-Free Money Market Fund/Service
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks as high a level of income, exempt from federal and Massachusetts personal income tax, as is consistent with the preservation of capital and liquidity.
Fee Table fmmt357057_FundFeesAndExpensesAbstract  
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 rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Annual class operating expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination at least one year from the effective date of the prospectus
Expense Example rr_ExpenseExampleAbstract  
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 mutual 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:
Portfolio Turnover fmmt357057_PortfolioTurnoverAltAbstract  
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 Massachusetts personal income taxes.
  • Potentially investing up to 20% of assets in municipal securities whose interest is subject to Massachusetts personal income tax.
  • Normally not investing in municipal securities whose interest is subject to the federal alternative minimum 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, 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.
  • 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 Massachusetts 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.

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. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
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.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.
Performance fmmt357057_FundPastPerformanceAbstract  
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.advisor.fidelity.com for updated return 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 Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance is not an indication of future performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Annual Total Returns rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Year-by-Year Returns

Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return0.54%March 31, 2008
Lowest Quarter Return0.00%March 31, 2010
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
For the periods ended
December 31, 2011
Service | Fidelity Massachusetts AMT Tax-Free Money Market Fund | Service Class
  
Shareholder Fees rr_ShareholderFeesAbstract  
Shareholder fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Annual class operating expenses rr_OperatingExpensesAbstract  
Management fee rr_ManagementFeesOverAssets 0.20%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.05%
Total annual operating expenses rr_ExpensesOverAssets 0.50%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.05% [3]
Total annual operating expenses after fee waiver and/or expense reimbursement rr_NetExpensesOverAssets 0.45%
Expense Example rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 46
3 years rr_ExpenseExampleYear03 144
5 years rr_ExpenseExampleYear05 252
10 years rr_ExpenseExampleYear10 567
Annual Total Returns rr_BarChartTableAbstract  
2008 rr_AnnualReturn2008 1.70%
2009 rr_AnnualReturn2009 0.09%
2010 rr_AnnualReturn2010 0.01%
2011 rr_AnnualReturn2011 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.54%
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2008
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Average Annual Total Returns rr_AverageAnnualReturnAbstract  
Label rr_AverageAnnualReturnLabel Service Class
Past 1 year rr_AverageAnnualReturnYear01 0.01%
Life of class rr_AverageAnnualReturnSinceInception 0.87% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 18, 2007
[1] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Institutional Class of the fund to the extent that total operating expenses (excluding interest, taxes, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.20%. This arrangement will remain in effect for at least one year from the effective date of the prospectus. FMR may not discontinue or modify this arrangement without the approval of the Board of Trustees.
[2] From April 18, 2007.
[3] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Service Class of the fund to the extent that total operating expenses (excluding interest, taxes, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.45%. This arrangement will remain in effect for at least one year from the effective date of the prospectus. FMR may not discontinue or modify this arrangement without the approval of the Board of Trustees.