485BPOS

As filed with the Securities and Exchange Commission on August 16, 2013

1933 Act File No. 2-92915

1940 Act File No. 811-4096

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C.  20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 57

AND REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 58

MFSÒ MUNICIPAL SERIES TRUST

(Exact Name of Registrant as Specified in Charter)

111 Huntington Avenue, Boston, Massachusetts 02199-7618

(Address of Principal Executive Offices)

Registrant’s Telephone Number, Including Area Code:  (617) 954-5000

Susan S. Newton, Massachusetts Financial Services Company,

111 Huntington Avenue, Boston, Massachusetts 02199-7618

(Name and Address of Agent for Service)

APPROXIMATE DATE OF PROPOSED PUBLIC OFFERING:

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

x immediately upon filing pursuant to paragraph (b)

o on [date] pursuant to paragraph (b)

o 60 days after filing pursuant to paragraph (a)(i)

o on [date] pursuant to paragraph (a)(i)

o 75 days after filing pursuant to paragraph (a)(ii)

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

If appropriate, check the following box:

o this post-effective amendment designates a new effective date for a previously filed post-effective amendment

NOTICE

Notice is hereby given that this Registration Statement has been executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually, and the obligations of or arising out of this Registration Statement are not binding upon any of the Trustees, officers, or shareholders of the Registrant individually, but are binding only upon the assets and property of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment to the Registration Statement to be signed on its behalf by the undersigned, thereto duly authorized, in the City of Boston and The Commonwealth of Massachusetts on the 16th day of August, 2013.

MFS® MUNICIPAL SERIES TRUST
By:	JOHN M. CORCORAN*
Name:	John M. Corcoran
Title:	President

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment to its Registration Statement has been signed below by the following persons in the capacities indicated on August 16, 2013.

SIGNATURE	TITLE
JOHN M. CORCORAN*	President (Principal Executive Officer)
John M. Corcoran
DAVID L. DILORENZO*	Principal Financial and Accounting Officer
David L. DiLorenzo
ROBERT E. BUTLER*	Trustee
Robert E. Butler
MAUREEN R. GOLDFARB*	Trustee
Maureen R. Goldfarb
DAVID H. GUNNING*	Trustee
David H. Gunning
WILLIAM R. GUTOW*	Trustee
William R. Gutow

MICHAEL HEGARTY*	Trustee
Michael Hegarty
JOHN P. KAVANAUGH*	Trustee
John P. Kavanaugh
ROBERT J. MANNING*	Trustee
Robert J. Manning
J. DALE SHERRATT*	Trustee
J. Dale Sherratt
LAURIE J. THOMSEN*	Trustee
Laurie J. Thomsen
ROBERT W. UEK*	Trustee
Robert W. Uek
	*By:	SUSAN S. NEWTON
	Name:	Susan S. Newton
		as Attorney-in-fact
	Executed by Susan S. Newton on behalf of those indicated pursuant to a Power of Attorney, dated December 7, 2012 (Trustees) and a Power of Attorney, dated December 7, 2012 (Corcoran) (DiLorenzo), filed herewith.

MFS Series Trust I

MFS Series Trust II

MFS Series Trust III

MFS Series Trust IV

MFS Series Trust V

MFS Series Trust VI

MFS Series Trust VII

MFS Series Trust VIII

MFS Series Trust IX

MFS Series Trust X

MFS Series Trust XI

MFS Series Trust XII

MFS Series Trust XIII

MFS Series Trust XIV

MFS Series Trust XV

MFS Series Trust XVI

Massachusetts Investors Growth Stock Fund

Massachusetts Investors Trust

MFS Institutional Trust

MFS Municipal Series Trust

MFS Variable Insurance Trust

MFS Variable Insurance Trust II

MFS Variable Insurance Trust III

MFS California Municipal Fund

MFS Charter Income Trust

MFS Government Markets Income Trust

MFS High Income Municipal Trust

MFS High Yield Municipal Trust

MFS InterMarket Income Trust I

MFS Intermediate High Income Fund

MFS Intermediate Income Trust

MFS Investment Grade Municipal Trust

MFS Multimarket Income Trust

MFS Municipal Income Trust

MFS Special Value Trust

(each a “Registrant”)

POWER OF ATTORNEY

The undersigned, a Trustee of each of the above-mentioned Registrants, hereby severally constitutes and appoints Mark N. Polebaum, Susan S. Newton,

Christopher R. Bohane, Thomas H. Connors, Brian E. Langenfeld and Susan A. Pereira, and each of them singly, as true and lawful attorneys, with full power to them and each of them to sign for each of the undersigned, in the names of, and in the capacities indicated below, any Registration Statement and any and all amendments thereto and to file the same with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission for the purpose of registering the Registrant as a management investment company under the Investment Company Act of 1940 and/or the shares issued by the Registrant under the Securities Act of 1933 granting unto my said attorneys, and each of them, acting alone, full power and authority to do and perform each and every act and thing requisite or necessary or desirable to be done in the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys or any of them may lawfully do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned have hereunto set their hand on this 7th day of December, 2012.

ROBERT E. BUTLER	Trustee
Robert E. Butler
MAUREEN R. GOLDFARB	Trustee
Maureen R. Goldfarb
DAVID H. GUNNING	Trustee
David H. Gunning
WILLIAM R. GUTOW	Trustee
William R. Gutow
MICHAEL HEGARTY	Trustee
Michael Hegarty
JOHN P. KAVANAUGH	Trustee
John P. Kavanaugh

ROBERT J. MANNING	Trustee
Robert J. Manning
J. DALE SHERRATT	Trustee
J. Dale Sherratt
LAURIE J. THOMSEN	Trustee
Laurie J. Thomsen
ROBERT W. UEK	Trustee
Robert W. Uek

MFS Series Trust I

MFS Series Trust II

MFS Series Trust III

MFS Series Trust IV

MFS Series Trust V

MFS Series Trust VI

MFS Series Trust VII

MFS Series Trust VIII

MFS Series Trust IX

MFS Series Trust X

MFS Series Trust XI

MFS Series Trust XII

MFS Series Trust XIII

MFS Series Trust XIV

MFS Series Trust XV

MFS Series Trust XVI

Massachusetts Investors Growth Stock Fund

Massachusetts Investors Trust

MFS Institutional Trust

MFS Municipal Series Trust

MFS Variable Insurance Trust

MFS Variable Insurance Trust II

MFS Variable Insurance Trust III

MFS California Municipal Fund

MFS Charter Income Trust

MFS Government Markets Income Trust

MFS High Income Municipal Trust

MFS High Yield Municipal Trust

MFS InterMarket Income Trust I

MFS Intermediate High Income Fund

MFS Intermediate Income Trust

MFS Investment Grade Municipal Trust

MFS Multimarket Income Trust

MFS Municipal Income Trust

MFS Special Value Trust

(each a “Registrant”)

POWER OF ATTORNEY

The undersigned, being the President and Principal Executive Officer, and Treasurer and Principal Financial and Accounting Officer, respectively, of each of the above-mentioned Registrants, hereby severally constitutes and appoints Mark N. Polebaum, Susan S. Newton, Christopher R. Bohane, Thomas H. Connors, Brian E.

Langenfeld and Susan A. Pereira, and each of them singly, as true and lawful attorneys, with full power to them and each of them to sign for each of the undersigned, in the names of, and in the capacities indicated below, any Registration Statement and any and all amendments thereto and to file the same with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission for the purpose of registering the Registrant as a management investment company under the Investment Company Act of 1940 and/or the shares issued by the Registrant under the Securities Act of 1933 granting unto my said attorneys, and each of them, acting alone, full power and authority to do and perform each and every act and thing requisite or necessary or desirable to be done in the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys or any of them may lawfully do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned have hereunto set their hand on this 7th day of December, 2012.

JOHN M. CORCORAN	President (Principal Executive Officer)
John M. Corcoran
DAVID L. DILORENZO	Principal Financial and Accounting Officer
David L. DiLorenzo

MFS MUNICIPAL SERIES TRUST

MFSÒ ALABAMA MUNICIPAL BOND FUND

MFSÒ ARKANSAS MUNICIPAL BOND FUND

MFSÒ CALIFORNIA MUNICIPAL BOND FUND

MFSÒ GEORGIA MUNICIPAL BOND FUND

MFSÒ MARYLAND MUNICIPAL BOND FUND

MFSÒ MASSACHUSETTS MUNICIPAL BOND FUND

MFSÒ MISSISSIPPI MUNICIPAL BOND FUND

MFSÒ MUNICIPAL INCOME FUND

MFSÒ NEW YORK MUNICIPAL BOND FUND

MFSÒ NORTH CAROLINA MUNICIPAL BOND FUND

MFSÒ PENNSYLVANIA MUNICIPAL BOND FUND

MFSÒ SOUTH CAROLINA MUNICIPAL BOND FUND

MFSÒ TENNESSEE MUNICIPAL BOND FUND

MFSÒ VIRGINIA MUNICIPAL BOND FUND

MFSÒ WEST VIRGINIA MUNICIPAL BOND FUND

INDEX TO EXHIBITS

EXHIBIT NO.	DESCRIPTION OF EXHIBIT	PAGE NO.
101	Risk/Return summary of each fund’s prospectus as an Interactive Data File using eXtensible Business Reporting Language (“XBRL”)

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Arkansas Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Arkansas, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 16% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

16.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Arkansas. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Arkansas.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Arkansas, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Because MFS may invest a relatively large percentage of the fund's assets in a single issuer or small number of issuers, the fund's performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.44)%. During the period(s) shown in the bar chart, the highest quarterly return was 5.87% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.49)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.44%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.87%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.49%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.71%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

544

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

722

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

915

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,472

Annual Return 2003

rr_AnnualReturn2003

4.53%

Annual Return 2004

rr_AnnualReturn2004

3.28%

Annual Return 2005

rr_AnnualReturn2005

3.09%

Annual Return 2006

rr_AnnualReturn2006

4.27%

Annual Return 2007

rr_AnnualReturn2007

3.15%

Annual Return 2008

rr_AnnualReturn2008

(3.23%)

Annual Return 2009

rr_AnnualReturn2009

13.80%

Annual Return 2010

rr_AnnualReturn2010

0.16%

Annual Return 2011

rr_AnnualReturn2011

10.29%

Annual Return 2012

rr_AnnualReturn2012

5.93%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

0.89%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.18%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.92%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

0.89%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.13%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.88%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.79%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.12%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.92%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.50%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

553

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

797

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,066

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,701

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

153

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

497

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

866

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,701

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.10%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.04%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.78%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

MFS Arkansas Municipal Bond Fund

MFS Arkansas Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Arkansas, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Arkansas Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Arkansas Municipal Bond Fund		A	B
Management Fee		0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%
Other Expenses		0.16%	0.16%
Total Annual Fund Operating Expenses		0.86%	1.61%
Fee Reductions and/or Expense Reimbursements	[1]	(0.15%)	(0.11%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.71%	1.50%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Arkansas Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	544	722	915	1,472
B	553	797	1,066	1,701

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Arkansas Municipal Bond Fund B	153	497	866	1,701

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 16% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Arkansas. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Arkansas.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Arkansas, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.44)%. During the period(s) shown in the bar chart, the highest quarterly return was 5.87% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.49)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Arkansas Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	1.10%	4.04%	3.78%
A	A Shares Returns Before Taxes	0.89%	4.18%	3.92%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	0.89%	4.13%	3.88%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	1.79%	4.12%	3.92%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

MFS California Municipal Bond Fund

MFS California Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of California, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS California Municipal Bond Fund	A		B	C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS California Municipal Bond Fund		A	B	C
Management Fee		0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%
Other Expenses		0.15%	0.15%	0.15%
Total Annual Fund Operating Expenses		0.85%	1.60%	1.60%
Fee Reductions and/or Expense Reimbursements	[1]	(0.15%)	(0.12%)	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.70%	1.48%	1.60%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS California Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	543	719	910	1,461
B	551	793	1,060	1,689
C	263	505	871	1,900

Expense Example No Redemption MFS California Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	151	493	860	1,689
C	163	505	871	1,900

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of California. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of California.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in California, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.80)%. During the period(s) shown in the bar chart, the highest quarterly return was 10.24% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (6.08)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS California Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	5.45%	4.79%	4.25%
C	C Shares Returns Before Taxes	8.28%	4.95%	3.94%
A	A Shares Returns Before Taxes	5.06%	4.89%	4.38%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	5.04%	4.89%	4.37%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	4.64%	4.80%	4.36%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Mississippi Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Mississippi, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

12.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Mississippi. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Mississippi.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Mississippi, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Because MFS may invest a relatively large percentage of the fund's assets in a single issuer or small number of issuers, the fund's performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

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Class A Bar Chart.

Bar Chart Narrative [Text Block]

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The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

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The total return for the six-month period ended June 30, 2013 was (2.61)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.60% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.18)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

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(2.61%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.60%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

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(5.18%)

Performance Table Heading

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Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

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Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

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Label

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Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

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6.78%

Average Annual Returns, 5 Years

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5.91%

Average Annual Returns, 10 Years

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5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.90%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.75%

Expenses Deferred Charges [Text Block]

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On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

548

Expense Example, with Redemption, 3 Years

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734

Expense Example, with Redemption, 5 Years

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936

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,517

Annual Return 2003

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4.88%

Annual Return 2004

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3.60%

Annual Return 2005

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3.46%

Annual Return 2006

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4.69%

Annual Return 2007

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2.92%

Annual Return 2008

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(2.81%)

Annual Return 2009

rr_AnnualReturn2009

13.65%

Annual Return 2010

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0.45%

Annual Return 2011

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10.43%

Annual Return 2012

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7.26%

Label

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A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.17%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.59%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.25%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.15%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.57%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.24%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.71%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.50%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.23%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.65%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.47%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

550

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

803

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,080

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,739

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

150

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

503

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

880

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,739

Label

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B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.51%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.53%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.12%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.00% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

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MFS Georgia Municipal Bond Fund

MFS Georgia Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Georgia, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Georgia Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Georgia Municipal Bond Fund		A	B
Management Fee		0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%
Other Expenses		0.26%	0.26%
Total Annual Fund Operating Expenses		0.96%	1.71%
Fee Reductions and/or Expense Reimbursements	[1]	(0.01%)	(0.01%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.95%	1.70%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Georgia Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	567	765	980	1,596
B	573	838	1,127	1,820

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Georgia Municipal Bond Fund B	173	538	927	1,820

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Georgia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Georgia.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Georgia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.92)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.91% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.23)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Georgia Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	3.32%	4.42%	3.96%
A	A Shares Returns Before Taxes	3.03%	4.54%	4.05%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	3.03%	4.45%	4.01%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	3.16%	4.41%	4.02%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.95% of the fund's average daily net assets annually for Class A shares, and 1.70% of the fund's average daily net assets annually for Class B shares. This written agreement will continue until at least July 31, 2014, after which MFS may increase such expense limitation to 1.00% of the fund's average daily net assets annually for Class A shares and 1.75% of the fund's average daily net assets annually for Class B shares without a vote of the fund's Board of Trustees, subject to certain conditions. Any increase above 1.00% of the fund's average daily net assets annually for Class A shares and 1.75% of the fund's average daily net assets annually for Class B shares would require a vote of the fund's Board of Trustees.

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MFS Virginia Municipal Bond Fund

MFS Virginia Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Virginia, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Virginia Municipal Bond Fund	A		B	C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Virginia Municipal Bond Fund	A	B	C
Management Fee	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%
Other Expenses	0.16%	0.16%	0.16%
Total Annual Fund Operating Expenses	0.86%	1.61%	1.61%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Virginia Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	559	736	929	1,485
B	564	808	1,076	1,710
C	264	508	876	1,911

Expense Example No Redemption MFS Virginia Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	164	508	876	1,710
C	164	508	876	1,911

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund 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.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Virginia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Virginia.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Virginia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013, was (3.68)%.  During the period(s) shown in the bar chart, the highest quarterly return was 6.69% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.48)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Virginia Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.38%	4.18%	4.07%
C	C Shares Returns Before Taxes	5.47%	4.53%	3.90%
A	A Shares Returns Before Taxes	2.08%	4.28%	4.11%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.08%	4.23%	4.09%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.57%	4.21%	4.10%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

MFS Maryland Municipal Bond Fund

MFS Maryland Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Maryland, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Maryland Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Maryland Municipal Bond Fund	A	B
Management Fee	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%
Other Expenses	0.22%	0.22%
Total Annual Fund Operating Expenses	0.92%	1.67%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Maryland Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	564	754	960	1,553
B	570	826	1,107	1,777

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Maryland Municipal Bond Fund B	170	526	907	1,777

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Maryland. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Maryland.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Maryland, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.21)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.51% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.24)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Maryland Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.24%	4.26%	3.84%
A	A Shares Returns Before Taxes	1.95%	4.34%	3.88%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	1.95%	4.32%	3.86%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.57%	4.29%	3.90%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Massachusetts Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Massachusetts, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

15.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Massachusetts. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Massachusetts.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Massachusetts, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (4.06)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.76% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.99)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.06%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.76%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.99%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.85%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

558

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

733

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

924

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,474

Annual Return 2003

rr_AnnualReturn2003

4.88%

Annual Return 2004

rr_AnnualReturn2004

4.09%

Annual Return 2005

rr_AnnualReturn2005

3.51%

Annual Return 2006

rr_AnnualReturn2006

4.25%

Annual Return 2007

rr_AnnualReturn2007

2.86%

Annual Return 2008

rr_AnnualReturn2008

(6.83%)

Annual Return 2009

rr_AnnualReturn2009

18.26%

Annual Return 2010

rr_AnnualReturn2010

(0.02%)

Annual Return 2011

rr_AnnualReturn2011

11.25%

Annual Return 2012

rr_AnnualReturn2012

7.97%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.85%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.73%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.33%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.80%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.66%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.26%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.07%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.59%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.25%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

563

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

805

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,071

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,699

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

163

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

505

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

871

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,699

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.16%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.66%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.28%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS West Virginia Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of West Virginia, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

14.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of West Virginia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of West Virginia.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in West Virginia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Because MFS may invest a relatively large percentage of the fund's assets in a single issuer or small number of issuers, the fund's performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.50)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.89% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.24)% (for the calendar quarter ended September 30, 2008).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.50%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.89%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.24%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.88%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

561

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

742

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

939

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,508

Annual Return 2003

rr_AnnualReturn2003

4.80%

Annual Return 2004

rr_AnnualReturn2004

3.58%

Annual Return 2005

rr_AnnualReturn2005

2.82%

Annual Return 2006

rr_AnnualReturn2006

4.26%

Annual Return 2007

rr_AnnualReturn2007

2.12%

Annual Return 2008

rr_AnnualReturn2008

(5.94%)

Annual Return 2009

rr_AnnualReturn2009

13.18%

Annual Return 2010

rr_AnnualReturn2010

1.59%

Annual Return 2011

rr_AnnualReturn2011

10.46%

Annual Return 2012

rr_AnnualReturn2012

6.38%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.33%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

3.90%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.70%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.33%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

3.86%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.67%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.02%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

3.85%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.71%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.63%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

566

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

814

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,087

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,732

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

166

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

514

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

887

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,732

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.59%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

3.83%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.65%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS California Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of California, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of California. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of California.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in California, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.80)%. During the period(s) shown in the bar chart, the highest quarterly return was 10.24% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (6.08)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.80%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.24%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(6.08%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.85%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.70%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

543

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

719

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

910

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,461

Annual Return 2003

rr_AnnualReturn2003

4.73%

Annual Return 2004

rr_AnnualReturn2004

4.71%

Annual Return 2005

rr_AnnualReturn2005

3.92%

Annual Return 2006

rr_AnnualReturn2006

4.83%

Annual Return 2007

rr_AnnualReturn2007

1.18%

Annual Return 2008

rr_AnnualReturn2008

(10.07%)

Annual Return 2009

rr_AnnualReturn2009

18.63%

Annual Return 2010

rr_AnnualReturn2010

0.84%

Annual Return 2011

rr_AnnualReturn2011

12.35%

Annual Return 2012

rr_AnnualReturn2012

10.29%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.06%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.89%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.38%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.04%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.89%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.37%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

4.64%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.80%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.36%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.60%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.12%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.48%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

551

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

793

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,060

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,689

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

151

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

493

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

860

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,689

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.45%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.79%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.25%

C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.60%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

263

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

505

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

871

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,900

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

163

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

505

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

871

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,900

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

8.28%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.95%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.94%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

MFS West Virginia Municipal Bond Fund

MFS West Virginia Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of West Virginia, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS West Virginia Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS West Virginia Municipal Bond Fund	A	B
Management Fee	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%
Other Expenses	0.18%	0.18%
Total Annual Fund Operating Expenses	0.88%	1.63%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS West Virginia Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	561	742	939	1,508
B	566	814	1,087	1,732

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS West Virginia Municipal Bond Fund B	166	514	887	1,732

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of West Virginia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of West Virginia.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in West Virginia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.50)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.89% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.24)% (for the calendar quarter ended September 30, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS West Virginia Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	1.59%	3.83%	3.65%
A	A Shares Returns Before Taxes	1.33%	3.90%	3.70%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	1.33%	3.86%	3.67%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.02%	3.85%	3.71%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS North Carolina Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of North Carolina, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

18.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of North Carolina. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of North Carolina.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in North Carolina, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013, was (3.74)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.27% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.02)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.74%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.27%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.02%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.14%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.84%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

557

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

730

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

919

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,463

Annual Return 2003

rr_AnnualReturn2003

4.81%

Annual Return 2004

rr_AnnualReturn2004

3.65%

Annual Return 2005

rr_AnnualReturn2005

3.19%

Annual Return 2006

rr_AnnualReturn2006

4.03%

Annual Return 2007

rr_AnnualReturn2007

2.75%

Annual Return 2008

rr_AnnualReturn2008

(4.49%)

Annual Return 2009

rr_AnnualReturn2009

14.59%

Annual Return 2010

rr_AnnualReturn2010

0.36%

Annual Return 2011

rr_AnnualReturn2011

11.05%

Annual Return 2012

rr_AnnualReturn2012

7.45%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.34%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.54%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.11%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.22%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.49%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.06%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.74%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.41%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.06%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.14%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.59%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

562

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

802

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,066

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1.688

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

162

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

502

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

866

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,688

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.57%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.45%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.06%

C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.14%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.59%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

262

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

502

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

866

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,889

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

162

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

502

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

866

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,889

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.56%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.78%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.91%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Alabama Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Alabama, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 10% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

10.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Alabama. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Alabama.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Alabama, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (2.73)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.11% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.40)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(2.73%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.11%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.40%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.93%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

565

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

763

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

978

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,594

Annual Return 2003

rr_AnnualReturn2003

5.45%

Annual Return 2004

rr_AnnualReturn2004

3.43%

Annual Return 2005

rr_AnnualReturn2005

2.72%

Annual Return 2006

rr_AnnualReturn2006

4.29%

Annual Return 2007

rr_AnnualReturn2007

3.35%

Annual Return 2008

rr_AnnualReturn2008

(5.13%)

Annual Return 2009

rr_AnnualReturn2009

15.26%

Annual Return 2010

rr_AnnualReturn2010

(0.03%)

Annual Return 2011

rr_AnnualReturn2011

10.22%

Annual Return 2012

rr_AnnualReturn2012

7.62%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.51%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.31%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.08%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.51%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.22%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.01%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.91%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.21%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.04%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.71%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.68%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

571

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

836

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,125

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,818

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

171

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

536

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

925

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,818

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.82%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.22%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.96%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.93% of the fund's average daily net assets annually for Class A shares and 1.68% of the fund's average daily net assets annually for Class B shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Maryland Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Maryland, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

23.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Maryland. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Maryland.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Maryland, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.21)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.51% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.24)% (for the calendar quarter ended December 31, 2008).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.21%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.51%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.24%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.22%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.92%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

564

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

754

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

960

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,553

Annual Return 2003

rr_AnnualReturn2003

4.92%

Annual Return 2004

rr_AnnualReturn2004

3.49%

Annual Return 2005

rr_AnnualReturn2005

3.10%

Annual Return 2006

rr_AnnualReturn2006

4.29%

Annual Return 2007

rr_AnnualReturn2007

1.41%

Annual Return 2008

rr_AnnualReturn2008

(8.51%)

Annual Return 2009

rr_AnnualReturn2009

18.42%

Annual Return 2010

rr_AnnualReturn2010

1.80%

Annual Return 2011

rr_AnnualReturn2011

9.96%

Annual Return 2012

rr_AnnualReturn2012

7.04%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.95%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.34%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.88%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.95%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.32%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.86%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.57%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.29%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.90%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.22%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.67%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

570

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

826

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,107

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,777

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

170

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

526

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

907

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,777

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.24%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.26%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.84%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Municipal Income Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-14 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

23.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (4.00)%. During the period(s) shown in the bar chart, the highest quarterly return was 8.54% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.04)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.00%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

8.54%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.04%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.40%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.80%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.77%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

550

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

715

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

895

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,415

Annual Return 2003

rr_AnnualReturn2003

5.91%

Annual Return 2004

rr_AnnualReturn2004

5.04%

Annual Return 2005

rr_AnnualReturn2005

3.97%

Annual Return 2006

rr_AnnualReturn2006

4.77%

Annual Return 2007

rr_AnnualReturn2007

2.61%

Annual Return 2008

rr_AnnualReturn2008

(7.59%)

Annual Return 2009

rr_AnnualReturn2009

18.05%

Annual Return 2010

rr_AnnualReturn2010

1.93%

Annual Return 2011

rr_AnnualReturn2011

10.62%

Annual Return 2012

rr_AnnualReturn2012

10.46%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.21%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.29%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.87%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.20%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.27%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.86%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

4.77%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.16%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.82%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.40%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.55%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.52%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

555

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

787

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,042

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,641

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

155

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

487

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

842

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,641

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.75%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.22%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.77%

C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fee

rr_ManagementFeesOverAssets

0.40%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.55%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.52%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

255

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

487

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

842

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,843

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

155

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

487

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

842

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,843

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

8.60%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.52%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.61%

I

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fee

rr_ManagementFeesOverAssets

0.40%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.55%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.52%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

53

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

173

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

304

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 686

Label

rr_AverageAnnualReturnLabel

I Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

10.74%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

6.55%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.63%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.37% of the fund's average daily net assets annually in excess of $1.3 billion up to $2 billion and 0.35% of the fund's average daily net assets annually in excess of $2.0 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

MFS Mississippi Municipal Bond Fund

MFS Mississippi Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Mississippi, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Mississippi Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Mississippi Municipal Bond Fund		A	B
Management Fee		0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%
Other Expenses		0.20%	0.20%
Total Annual Fund Operating Expenses		0.90%	1.65%
Fee Reductions and/or Expense Reimbursements	[1]	(0.15%)	(0.18%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.75%	1.47%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Mississippi Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	548	734	936	1,517
B	550	803	1,080	1,739

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Mississippi Municipal Bond Fund B	150	503	880	1,739

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Mississippi. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Mississippi.

The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund’s assets in a single issuer or a small number of issuers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Mississippi, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund’s assets in a single issuer or small number of issuers, the fund’s performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (2.61)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.60% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.18)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Mississippi Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.51%	4.53%	4.12%
A	A Shares Returns Before Taxes	2.17%	4.59%	4.25%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.15%	4.57%	4.24%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.71%	4.50%	4.23%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.00% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

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MFS New York Municipal Bond Fund

MFS New York Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of New York, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS New York Municipal Bond Fund	A		B	C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS New York Municipal Bond Fund	A	B	C
Management Fee	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%
Other Expenses	0.16%	0.16%	0.16%
Total Annual Fund Operating Expenses	0.86%	1.61%	1.61%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS New York Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	559	736	929	1,485
B	564	808	1,076	1,710
C	264	508	876	1,911

Expense Example No Redemption MFS New York Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	164	508	876	1,710
C	164	508	876	1,911

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of New York. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of New York.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in New York, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (4.21)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.23% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.80)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS New York Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	3.87%	4.33%	4.01%
C	C Shares Returns Before Taxes	6.76%	4.63%	3.85%
A	A Shares Returns Before Taxes	3.50%	4.42%	4.13%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	3.50%	4.38%	4.08%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	3.55%	4.34%	4.10%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

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MFS Alabama Municipal Bond Fund

MFS Alabama Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Alabama, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Alabama Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Alabama Municipal Bond Fund		A	B
Management Fee		0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%
Other Expenses		0.26%	0.26%
Total Annual Fund Operating Expenses		0.96%	1.71%
Fee Reductions and/or Expense Reimbursements	[1]	(0.03%)	(0.03%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.93%	1.68%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Alabama Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	565	763	978	1,594
B	571	836	1,125	1,818

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Alabama Municipal Bond Fund B	171	536	925	1,818

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 10% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Alabama. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Alabama.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Alabama, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (2.73)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.11% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.40)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Alabama Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.82%	4.22%	3.96%
A	A Shares Returns Before Taxes	2.51%	4.31%	4.08%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.51%	4.22%	4.01%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.91%	4.21%	4.04%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.93% of the fund's average daily net assets annually for Class A shares and 1.68% of the fund's average daily net assets annually for Class B shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

Class A1 and B1 Prospectus | MFS Municipal Income Fund

MFS Municipal Income Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-14 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees Class A1 and B1 Prospectus MFS Municipal Income Fund	A1		B1
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses Class A1 and B1 Prospectus MFS Municipal Income Fund		A1	B1
Management Fee		0.40%	0.40%
Distribution and/or Service (12b-1) Fees		none	1.00%
Other Expenses		0.15%	0.15%
Total Annual Fund Operating Expenses		0.55%	1.55%
Fee Reductions and/or Expense Reimbursements	[1]	(0.03%)	(0.27%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.52%	1.28%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example Class A1 and B1 Prospectus MFS Municipal Income Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A1	526	640	765	1,129
B1	530	763	1,019	1,552

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
Class A1 and B1 Prospectus MFS Municipal Income Fund B1	130	463	819	1,552

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A1 Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.99)%. During the period(s) shown in the bar chart, the highest quarterly return was 8.59% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.86)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns Class A1 and B1 Prospectus MFS Municipal Income Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B1	B1 Shares Returns Before Taxes	5.90%	5.46%	5.02%
A1	A1 Shares Returns Before Taxes	5.47%	5.58%	5.15%
After Taxes on Distributions A1	A1 Shares Returns After Taxes on Distributions	5.46%	5.56%	5.14%
After Taxes on Distributions and Sale of Fund Shares A1	A1 Shares Returns After Taxes on Distributions and Sale of Fund Shares	5.02%	5.44%	5.08%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.37% of the fund's average daily net assets annually in excess of $1.3 billion up to $2 billion and 0.35% of the fund's average daily net assets annually in excess of $2.0 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B1 shares, assets attributable to such Class B1 shares are subject to the Class B1 service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B1 shares, the fund's distributor, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B1 service fee to 0.00% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS New York Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of New York, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

18.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of New York. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of New York.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in New York, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (4.21)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.23% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.80)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.21%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.23%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.80%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

559

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

736

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

929

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,485

Annual Return 2003

rr_AnnualReturn2003

4.77%

Annual Return 2004

rr_AnnualReturn2004

3.82%

Annual Return 2005

rr_AnnualReturn2005

3.04%

Annual Return 2006

rr_AnnualReturn2006

4.34%

Annual Return 2007

rr_AnnualReturn2007

3.22%

Annual Return 2008

rr_AnnualReturn2008

(6.97%)

Annual Return 2009

rr_AnnualReturn2009

17.00%

Annual Return 2010

rr_AnnualReturn2010

0.84%

Annual Return 2011

rr_AnnualReturn2011

9.27%

Annual Return 2012

rr_AnnualReturn2012

8.66%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.50%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.42%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.13%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.50%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.38%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.08%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.55%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.34%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.10%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

564

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

808

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,076

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,710

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

164

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

508

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

876

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,710

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.87%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.33%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.01%

C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

264

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

508

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

876

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,911

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

164

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

508

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

876

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,911

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.76%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.63%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.85%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Prospectus Date	rr_ProspectusDate	Jul. 29, 2013

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS South Carolina Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of South Carolina, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

15.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of South Carolina. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of South Carolina.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in South Carolina, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.82)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.07% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.81)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.82%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.07%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.81%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

559

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

736

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

929

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,485

Annual Return 2003

rr_AnnualReturn2003

5.04%

Annual Return 2004

rr_AnnualReturn2004

3.59%

Annual Return 2005

rr_AnnualReturn2005

3.45%

Annual Return 2006

rr_AnnualReturn2006

4.26%

Annual Return 2007

rr_AnnualReturn2007

2.27%

Annual Return 2008

rr_AnnualReturn2008

(5.99%)

Annual Return 2009

rr_AnnualReturn2009

15.15%

Annual Return 2010

rr_AnnualReturn2010

0.48%

Annual Return 2011

rr_AnnualReturn2011

9.71%

Annual Return 2012

rr_AnnualReturn2012

7.60%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.49%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.11%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.91%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.49%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.10%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.91%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.80%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.07%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.92%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

564

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

808

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,076

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,710

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

164

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

508

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

876

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,710

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.89%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.05%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.87%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

MFS Massachusetts Municipal Bond Fund

MFS Massachusetts Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Massachusetts, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Massachusetts Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Massachusetts Municipal Bond Fund	A	B
Management Fee	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%
Other Expenses	0.15%	0.15%
Total Annual Fund Operating Expenses	0.85%	1.60%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Massachusetts Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	558	733	924	1,474
B	563	805	1,071	1,699

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Massachusetts Municipal Bond Fund B	163	505	871	1,699

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Massachusetts. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Massachusetts.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Massachusetts, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (4.06)%. During the period(s) shown in the bar chart, the highest quarterly return was 7.76% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.99)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Massachusetts Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	3.16%	4.66%	4.28%
A	A Shares Returns Before Taxes	2.85%	4.73%	4.33%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.80%	4.66%	4.26%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	3.07%	4.59%	4.25%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

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Class A, B, C, and I Prospectus | MFS Municipal Income Fund

MFS Municipal Income Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-14 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees Class A, B, C, and I Prospectus MFS Municipal Income Fund	A		B	C	I
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses Class A, B, C, and I Prospectus MFS Municipal Income Fund		A	B	C	I
Management Fee		0.40%	0.40%	0.40%	0.40%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses		0.15%	0.15%	0.15%	0.15%
Total Annual Fund Operating Expenses		0.80%	1.55%	1.55%	0.55%
Fee Reductions and/or Expense Reimbursements	[1]	(0.03%)	(0.03%)	(0.03%)	(0.03%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.77%	1.52%	1.52%	0.52%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example Class A, B, C, and I Prospectus MFS Municipal Income Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	550	715	895	1,415
B	555	787	1,042	1,641
C	255	487	842	1,843
I	53	173	304	686

Expense Example No Redemption Class A, B, C, and I Prospectus MFS Municipal Income Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	155	487	842	1,641
C	155	487	842	1,843

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (4.00)%. During the period(s) shown in the bar chart, the highest quarterly return was 8.54% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.04)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns Class A, B, C, and I Prospectus MFS Municipal Income Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	5.75%	5.22%	4.77%
C	C Shares Returns Before Taxes	8.60%	5.52%	4.61%
I	I Shares Returns Before Taxes	10.74%	6.55%	5.63%
A	A Shares Returns Before Taxes	5.21%	5.29%	4.87%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	5.20%	5.27%	4.86%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	4.77%	5.16%	4.82%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.37% of the fund's average daily net assets annually in excess of $1.3 billion up to $2 billion and 0.35% of the fund's average daily net assets annually in excess of $2.0 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

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MFS Pennsylvania Municipal Bond Fund

MFS Pennsylvania Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Pennsylvania, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 7 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Pennsylvania Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Pennsylvania Municipal Bond Fund		A	B
Management Fee		0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%
Other Expenses		0.19%	0.19%
Total Annual Fund Operating Expenses		0.89%	1.64%
Fee Reductions and/or Expense Reimbursements	[1]	(0.15%)	(0.12%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		0.74%	1.52%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Pennsylvania Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	547	731	931	1,506
B	555	806	1,080	1,733

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Pennsylvania Municipal Bond Fund B	155	506	880	1,733

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Pennsylvania. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Pennsylvania.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Pennsylvania, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.77)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.97% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.72)% (for the calendar quarter ended September 30, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Pennsylvania Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	4.35%	4.40%	4.14%
A	A Shares Returns Before Taxes	4.10%	4.53%	4.27%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	4.10%	4.53%	4.27%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	3.98%	4.45%	4.24%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

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MFS Tennessee Municipal Bond Fund

MFS Tennessee Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Tennessee, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Tennessee Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS Tennessee Municipal Bond Fund	A	B
Management Fee	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%
Other Expenses	0.20%	0.20%
Total Annual Fund Operating Expenses	0.90%	1.65%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS Tennessee Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	562	748	950	1,530
B	568	820	1,097	1,754

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Tennessee Municipal Bond Fund B	168	520	897	1,754

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Tennessee. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Tennessee.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Tennessee, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (4.02)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.48% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.76)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS Tennessee Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	3.18%	4.36%	3.98%
A	A Shares Returns Before Taxes	2.85%	4.43%	4.04%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.85%	4.37%	3.98%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	3.08%	4.32%	3.99%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

MFS South Carolina Municipal Bond Fund

MFS South Carolina Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of South Carolina, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS South Carolina Municipal Bond Fund	A		B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS South Carolina Municipal Bond Fund	A	B
Management Fee	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%
Other Expenses	0.16%	0.16%
Total Annual Fund Operating Expenses	0.86%	1.61%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS South Carolina Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	559	736	929	1,485
B	564	808	1,076	1,710

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS South Carolina Municipal Bond Fund B	164	508	876	1,710

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of South Carolina. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of South Carolina.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in South Carolina, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013 was (3.82)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.07% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.81)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS South Carolina Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.89%	4.05%	3.87%
A	A Shares Returns Before Taxes	2.49%	4.11%	3.91%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.49%	4.10%	3.91%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.80%	4.07%	3.92%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Georgia Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Georgia, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

14.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Georgia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Georgia.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Georgia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.92)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.91% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.23)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.92%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.91%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.23%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.95%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

567

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

765

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

980

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,596

Annual Return 2003

rr_AnnualReturn2003

4.87%

Annual Return 2004

rr_AnnualReturn2004

3.56%

Annual Return 2005

rr_AnnualReturn2005

2.57%

Annual Return 2006

rr_AnnualReturn2006

4.00%

Annual Return 2007

rr_AnnualReturn2007

2.82%

Annual Return 2008

rr_AnnualReturn2008

(5.20%)

Annual Return 2009

rr_AnnualReturn2009

15.68%

Annual Return 2010

rr_AnnualReturn2010

0.00%

Annual Return 2011

rr_AnnualReturn2011

10.52%

Annual Return 2012

rr_AnnualReturn2012

8.16%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.03%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.54%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.05%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.03%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.45%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.01%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.16%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.41%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.02%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.26%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.71%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.70%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

573

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

838

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,127

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,820

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

173

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

538

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

927

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,820

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.32%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.42%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.96%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.95% of the fund's average daily net assets annually for Class A shares, and 1.70% of the fund's average daily net assets annually for Class B shares. This written agreement will continue until at least July 31, 2014, after which MFS may increase such expense limitation to 1.00% of the fund's average daily net assets annually for Class A shares and 1.75% of the fund's average daily net assets annually for Class B shares without a vote of the fund's Board of Trustees, subject to certain conditions. Any increase above 1.00% of the fund's average daily net assets annually for Class A shares and 1.75% of the fund's average daily net assets annually for Class B shares would require a vote of the fund's Board of Trustees.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Tennessee Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Tennessee, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Tennessee. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Tennessee.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Tennessee, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (4.02)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.48% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.76)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.02%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.48%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.76%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.90%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

562

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

748

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

950

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,530

Annual Return 2003

rr_AnnualReturn2003

4.69%

Annual Return 2004

rr_AnnualReturn2004

3.75%

Annual Return 2005

rr_AnnualReturn2005

2.94%

Annual Return 2006

rr_AnnualReturn2006

3.88%

Annual Return 2007

rr_AnnualReturn2007

3.00%

Annual Return 2008

rr_AnnualReturn2008

(5.45%)

Annual Return 2009

rr_AnnualReturn2009

15.10%

Annual Return 2010

rr_AnnualReturn2010

0.79%

Annual Return 2011

rr_AnnualReturn2011

10.09%

Annual Return 2012

rr_AnnualReturn2012

7.97%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.85%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.43%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.04%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.85%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.37%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.98%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.08%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.32%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.99%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.65%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

568

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

820

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,097

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,754

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

168

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

520

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

897

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,754

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.18%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.36%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.98%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Pennsylvania Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Pennsylvania, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 7 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

15.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Pennsylvania. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Pennsylvania.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Pennsylvania, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013 was (3.77)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.97% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.72)% (for the calendar quarter ended September 30, 2008).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.77%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.97%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.72%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.19%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.89%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.74%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

547

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

731

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

931

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,506

Annual Return 2003

rr_AnnualReturn2003

5.07%

Annual Return 2004

rr_AnnualReturn2004

4.00%

Annual Return 2005

rr_AnnualReturn2005

3.81%

Annual Return 2006

rr_AnnualReturn2006

4.87%

Annual Return 2007

rr_AnnualReturn2007

2.36%

Annual Return 2008

rr_AnnualReturn2008

(6.89%)

Annual Return 2009

rr_AnnualReturn2009

16.50%

Annual Return 2010

rr_AnnualReturn2010

1.03%

Annual Return 2011

rr_AnnualReturn2011

9.37%

Annual Return 2012

rr_AnnualReturn2012

9.30%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

4.10%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.53%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.27%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

4.10%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.53%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.27%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

3.98%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.45%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.24%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.19%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.64%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.12%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.52%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

555

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

806

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,080

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,733

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

155

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

506

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

880

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,733

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

4.35%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.40%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.14%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] MFS Fund Distributors, Inc., has agreed in writing to waive the Class A service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B shares, assets attributable to such Class B shares are subject to the Class B service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B shares, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B service fee to 0.10% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.

XML

MFS North Carolina Municipal Bond Fund

MFS North Carolina Municipal Bond Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of North Carolina, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS North Carolina Municipal Bond Fund	A		B	C
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	4.00%	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses MFS North Carolina Municipal Bond Fund	A	B	C
Management Fee	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%
Other Expenses	0.14%	0.14%	0.14%
Total Annual Fund Operating Expenses	0.84%	1.59%	1.59%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example MFS North Carolina Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	557	730	919	1,463
B	562	802	1,066	1.688
C	262	502	866	1,889

Expense Example No Redemption MFS North Carolina Municipal Bond Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	162	502	866	1,688
C	162	502	866	1,889

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.

Principal Investment Strategies

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of North Carolina. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of North Carolina.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in North Carolina, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Class A Bar Chart.

The total return for the six-month period ended June 30, 2013, was (3.74)%. During the period(s) shown in the bar chart, the highest quarterly return was 6.27% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (5.02)% (for the calendar quarter ended December 31, 2010).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns MFS North Carolina Municipal Bond Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	2.57%	4.45%	4.06%
C	C Shares Returns Before Taxes	5.56%	4.78%	3.91%
A	A Shares Returns Before Taxes	2.34%	4.54%	4.11%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	2.22%	4.49%	4.06%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	2.74%	4.41%	4.06%
Barclays Municipal Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index	6.78%	5.91%	5.10%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

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Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Virginia Municipal Bond Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax and personal income tax, if any, of Virginia, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-29 of the fund’s statement of additional information Part I.

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 higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund 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%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax and personal income tax, if any, of Virginia. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS may invest 25% or more of the fund’s assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water or sewers. Municipal instruments whose interest is exempt from federal and state personal income tax include instruments issued by U.S. territories and possessions (such as Puerto Rico, Guam, and the U.S. Virgin Islands) and their political subdivisions and public corporations. Although MFS seeks to invest the fund’s assets in municipal instruments whose interest is exempt from federal and state personal income tax, MFS may also invest in taxable instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS invests a large percentage of the fund’s assets in municipal issuers of Virginia.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Geographic Focus Risk:  The fund’s performance will be closely tied to the economic and political conditions in Virginia, and can be more volatile than the performance of a more geographically diversified fund. In addition, the fund’s performance can also be tied to the economic and political conditions of U.S. territories and possessions. These conditions may include constitutional or statutory limits on an issuer’s ability to raise revenues or increase taxes, anticipated or actual budget deficits or other financial difficulties, or changes in the credit quality of municipal issuers in the state or in U.S. territories and possessions.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-225-2606

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

mfs.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Bar Chart.

Bar Chart Narrative [Text Block]

rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2013, was (3.68)%.  During the period(s) shown in the bar chart, the highest quarterly return was 6.69% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.48)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.68%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.69%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.48%)

Performance Table Heading

rr_PerformanceTableHeading

Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

6.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.91%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

5.10%

A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

559

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

736

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

929

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,485

Annual Return 2003

rr_AnnualReturn2003

5.36%

Annual Return 2004

rr_AnnualReturn2004

4.23%

Annual Return 2005

rr_AnnualReturn2005

3.35%

Annual Return 2006

rr_AnnualReturn2006

4.03%

Annual Return 2007

rr_AnnualReturn2007

2.80%

Annual Return 2008

rr_AnnualReturn2008

(5.47%)

Annual Return 2009

rr_AnnualReturn2009

15.88%

Annual Return 2010

rr_AnnualReturn2010

0.51%

Annual Return 2011

rr_AnnualReturn2011

9.70%

Annual Return 2012

rr_AnnualReturn2012

7.17%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.08%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.28%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.11%

A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.08%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.23%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.09%

A | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

A Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.57%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.21%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.10%

B

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

564

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

808

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,076

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,710

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

164

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

508

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

876

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,710

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.38%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.18%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.07%

C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fee

rr_ManagementFeesOverAssets

0.45%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.16%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.61%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

264

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

508

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

876

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,911

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

164

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

508

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

876

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,911

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

5.47%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.53%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.90%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

XML

Document and Entity Information	0 Months Ended
	Mar. 31, 2013
Risk/Return:
Document Type	485BPOS
Document Period End Date	Mar. 31, 2013
Registrant Name	MFS MUNICIPAL SERIES TRUST
Central Index Key	0000751656
Amendment Flag	false
Document Creation Date	Jul. 26, 2013
Document Effective Date	Jul. 29, 2013
Prospectus Date	Jul. 29, 2013
MFS Alabama Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFALX
MFS Alabama Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBABX
MFS Arkansas Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFARX
MFS Arkansas Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBARX
MFS California Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MCFTX
MFS California Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBCAX
MFS California Municipal Bond Fund | C
Risk/Return:
Trading Symbol	MCCAX
MFS Georgia Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MMGAX
MFS Georgia Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBGAX
MFS Maryland Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFSMX
MFS Maryland Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBMDX
MFS Massachusetts Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFSSX
MFS Massachusetts Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBMAX
MFS Mississippi Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MISSX
MFS Mississippi Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBMSX
MFS New York Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MSNYX
MFS New York Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBNYX
MFS New York Municipal Bond Fund | C
Risk/Return:
Trading Symbol	MCNYX
MFS North Carolina Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MSNCX
MFS North Carolina Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBNCX
MFS North Carolina Municipal Bond Fund | C
Risk/Return:
Trading Symbol	MCNCX
MFS Pennsylvania Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFPAX
MFS Pennsylvania Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBPAX
MFS South Carolina Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFSCX
MFS South Carolina Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBSCX
MFS Tennessee Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MSTNX
MFS Tennessee Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBTNX
MFS Virginia Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MSVAX
MFS Virginia Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBVAX
MFS Virginia Municipal Bond Fund | C
Risk/Return:
Trading Symbol	MVACX
MFS West Virginia Municipal Bond Fund | A
Risk/Return:
Trading Symbol	MFWVX
MFS West Virginia Municipal Bond Fund | B
Risk/Return:
Trading Symbol	MBWVX
Class A, B, C, and I Prospectus | MFS Municipal Income Fund | A
Risk/Return:
Trading Symbol	MFIAX
Class A, B, C, and I Prospectus | MFS Municipal Income Fund | B
Risk/Return:
Trading Symbol	MMIBX
Class A, B, C, and I Prospectus | MFS Municipal Income Fund | C
Risk/Return:
Trading Symbol	MMICX
Class A, B, C, and I Prospectus | MFS Municipal Income Fund | I
Risk/Return:
Trading Symbol	MIMIX
Class A1 and B1 Prospectus | MFS Municipal Income Fund | A1
Risk/Return:
Trading Symbol	MMIDX
Class A1 and B1 Prospectus | MFS Municipal Income Fund | B1
Risk/Return:
Trading Symbol	MMIGX

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Municipal Income Fund Summary of Key Information

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek total return with an emphasis on income exempt from federal income tax, but also considering capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund.

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 8 of the fund’s prospectus and “Waivers of Sales Charges” on page I-14 of the fund’s statement of additional information Part I.

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):

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

2014-07-31

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 shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 23% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

23.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund invests, under normal market conditions, at least 80% of its net assets in securities and other investments, the interest on which is exempt from federal income tax. Interest from the fund’s investments may be subject to the federal alternative minimum tax.

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in municipal instruments.

MFS primarily invests the fund’s assets in investment grade debt instruments, but may also invest in less than investment grade quality debt instruments (lower quality debt instruments).

MFS may invest 25% or more of the fund’s total assets in municipal instruments that finance similar projects, such as those relating to education, healthcare, housing, utilities, water, or sewers.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual instruments and their issuers. Quantitative models that systematically evaluate instruments may also be considered. In structuring the fund, MFS may also consider top-down factors.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Interest Rate Risk:  The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

The credit quality of, and the ability to pay principal and interest when due by, an issuer of a municipal instrument depends on the credit quality of the entity supporting the municipal instrument, how essential any services supported by the municipal instrument are, the sufficiency of any revenues or taxes that support the municipal instrument, and/or the willingness or ability of the appropriate government entity to approve any appropriations necessary to support the municipal instrument.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Municipal Risk:  The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Prepayment/Extension Risk:  Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Derivatives Risk:  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk:  Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

Risk Lose Money [Text]

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As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.

Risk Not Insured Depository Institution [Text]

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An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.

The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.

Performance Availability Phone [Text]

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1-800-225-2606

Performance Availability Website Address [Text]

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mfs.com

Performance Past Does Not Indicate Future [Text]

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The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.

Bar Chart [Heading]

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Class A1 Bar Chart.

Bar Chart Narrative [Text Block]

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The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Does Not Reflect Sales Loads [Text]

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The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

Bar Chart Closing [Text Block]

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The total return for the six-month period ended June 30, 2013 was (3.99)%. During the period(s) shown in the bar chart, the highest quarterly return was 8.59% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (4.86)% (for the calendar quarter ended December 31, 2010).

Year to Date Return, Label

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The total return for the six-month period ended

Bar Chart, Year to Date Return, Date

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Jun. 30, 2013

Bar Chart, Year to Date Return

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(3.99%)

Highest Quarterly Return, Label

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highest quarterly return

Highest Quarterly Return, Date

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Sep. 30, 2009

Highest Quarterly Return

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8.59%

Lowest Quarterly Return, Label

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lowest quarterly return

Lowest Quarterly Return, Date

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Dec. 31, 2010

Lowest Quarterly Return

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(4.86%)

Performance Table Heading

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Performance Table.

Index No Deduction for Fees, Expenses, Taxes [Text]

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Reflects no deduction for fees, expenses or taxes

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.

Performance Table Closing [Text Block]

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown.

Caption

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Average Annual Total Returns (for the Periods Ended December 31, 2012)

Barclays Municipal Bond Index

Risk/Return:

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Label

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Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays Municipal Bond Index

Average Annual Returns, 1 Year

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6.78%

Average Annual Returns, 5 Years

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5.91%

Average Annual Returns, 10 Years

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5.10%

A1

Risk/Return:

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Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

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4.75%

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

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1.00%

^[1]

Management Fee

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0.40%

Distribution and/or Service (12b-1) Fees

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none

Other Expenses

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0.15%

Total Annual Fund Operating Expenses

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0.55%

Fee Reductions and/or Expense Reimbursements

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(0.03%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

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0.52%

Expenses Deferred Charges [Text Block]

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On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

Expense Example, with Redemption, 1 Year

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526

Expense Example, with Redemption, 3 Years

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640

Expense Example, with Redemption, 5 Years

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765

Expense Example, with Redemption, 10 Years

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1,129

Annual Return 2008

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(7.36%)

Annual Return 2009

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18.48%

Annual Return 2010

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2.19%

Annual Return 2011

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10.89%

Annual Return 2012

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10.73%

Label

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A1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

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5.47%

Average Annual Returns, 5 Years

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5.58%

Average Annual Returns, 10 Years

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5.15%

A1 | After Taxes on Distributions

Risk/Return:

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Label

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A1 Shares Returns After Taxes on Distributions

Average Annual Returns, 1 Year

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5.46%

Average Annual Returns, 5 Years

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5.56%

Average Annual Returns, 10 Years

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5.14%

A1 | After Taxes on Distributions and Sale of Fund Shares

Risk/Return:

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Label

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A1 Shares Returns After Taxes on Distributions and Sale of Fund Shares

Average Annual Returns, 1 Year

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5.02%

Average Annual Returns, 5 Years

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5.44%

Average Annual Returns, 10 Years

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5.08%

B1

Risk/Return:

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Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)

rr_MaximumDeferredSalesChargeOverOther

4.00%

Management Fee

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0.40%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

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0.15%

Total Annual Fund Operating Expenses

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1.55%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.27%)

^[2]

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

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1.28%

Expense Example, with Redemption, 1 Year

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530

Expense Example, with Redemption, 3 Years

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763

Expense Example, with Redemption, 5 Years

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1,019

Expense Example, with Redemption, 10 Years

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1,552

Expense Example, No Redemption, 1 Year

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130

Expense Example, No Redemption, 3 Years

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463

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

819

Expense Example, No Redemption, 10 Years

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$ 1,552

Label

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B1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

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5.90%

Average Annual Returns, 5 Years

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5.46%

Average Annual Returns, 10 Years

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5.02%

[1] On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.

[2] Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.37% of the fund's average daily net assets annually in excess of $1.3 billion up to $2 billion and 0.35% of the fund's average daily net assets annually in excess of $2.0 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, for one year from the date of purchase of Class B1 shares, assets attributable to such Class B1 shares are subject to the Class B1 service fee of 0.25% of the fund's average daily net assets annually. On assets attributable to all other Class B1 shares, the fund's distributor, MFS Fund Distributors, Inc., has agreed in writing to waive the Class B1 service fee to 0.00% of the fund's average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014. In addition, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 2014.