485BPOS

As filed with the Securities and Exchange Commission on July 19, 2013

1933 Act File No. 2-74959  

1940 Act File No. 811-3327

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C.  20549

FORM N-1A

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 54

AND

REGISTRATION STATEMENT UNDER

THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 49

MFS® SERIES TRUST XIII

(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

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 19th day of July 2013.

MFS® SERIES TRUST XIII
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 July 19, 2013.

SIGNATURE	TITLE
JOHN M. CORCORAN*	President (Principal Executive Officer)
John M. Corcoran
DAVID L. DILORENZO*	Principal Financial Officer 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® SERIES TRUST XIII

MFS® DIVERSIFIED INCOME FUND

MFS® GLOBAL REAL ESTATE FUND

MFS® GOVERNMENT SECURITIES FUND

MFS® NEW DISCOVERY VALUE 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 Global Real Estate 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.

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. The annual fund operating expenses for Class B, Class C, Class R1, Class R2, Class R3, and Class R4 shares are based on estimated “Other Expenses” for the current fiscal year expressed as a percentage of the fund’s estimated average net assets during the period.

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-13 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 46% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

46.00%

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

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in U.S. and foreign real estate-related investments.

MFS normally invests the fund’s assets primarily in equity securities.

MFS generally focuses the fund’s investments in equity real estate investment trusts (“REITs”) as well as similar entities formed under the laws of non-U.S. countries, but may also invest in mortgage REITs, hybrid REITs and other U.S. and foreign real estate-related investments, including emerging market real estate-related investments.

MFS may invest the fund’s assets in real estate-related investments of any size.  However, issuers of real estate-related investments tend to be small-to-medium-sized.

MFS typically allocates the fund’s investments across various geographic areas, REIT managers and property types, but may from time to time focus the fund’s investments in any one or a few of these areas.

MFS may invest a large percentage of the fund’s assets in issuers in a single country, a small number of countries, or a particular geographic region.

MFS selects investments by analyzing the fundamental and relative values of potential investments.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in U.S. and foreign real estate-related investments.

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:

Real Estate-Related Investment Risk:  The fund’s performance will be closely tied to the performance of real estate-related investments and as a result, can be more volatile than the performance of more broadly-diversified funds. The risks of investing in real estate-related investments include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.

Small to Medium Cap Risk:  The securities of small and medium-sized real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Currency Risk:  The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, and other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency.

Geographic Concentration Risk: The fund’s performance could be closely tied to the market, currency, economic, political, regulatory, geopolitical, and other conditions in the countries or regions in which the fund invests and could be more volatile than the performance of more geographically-diversified funds.

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.

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 three-month period ended March 31, 2013 was 5.59%. During the period(s) shown in the bar chart, the highest quarterly return was 18.70% (for the calendar quarter ended September 30, 2010) and the lowest quarterly return was (18.05)% (for the calendar quarter ended September 30, 2011).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the three-month period

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

5.59%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.70%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(18.05%)

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)

FTSE EPRA/NAREIT Developed Real Estate Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) FTSE EPRA/NAREIT Developed Real Estate Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

28.65%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

32.27%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

A

Risk/Return:

rr_RiskReturnAbstract

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.23%

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

693

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

943

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,212

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,978

Annual Return 2010

rr_AnnualReturn2010

15.29%

Annual Return 2011

rr_AnnualReturn2011

(7.22%)

Annual Return 2012

rr_AnnualReturn2012

29.49%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

22.04%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

27.87%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

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

19.76%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

22.05%

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

14.89%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

21.04%

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

601

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

921

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,268

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,113

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

201

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

621

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,068

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,113

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

24.40%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

28.50%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

301

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

621

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,068

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,306

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

201

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

621

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,068

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,306

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

27.40%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

28.89%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

100

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

312

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

542

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,201

Label

rr_AverageAnnualReturnLabel

I Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

29.68%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

30.18%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

R1

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

201

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

621

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,068

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,306

Label

rr_AverageAnnualReturnLabel

R1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

28.40%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

28.89%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

R2

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.48%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

151

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

468

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

808

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,768

Label

rr_AverageAnnualReturnLabel

R2 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

29.04%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

29.53%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

R3

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.23%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

125

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

390

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

676

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,489

Label

rr_AverageAnnualReturnLabel

R3 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

29.36%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

29.85%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

R4

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

100

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

312

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

542

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,201

Label

rr_AverageAnnualReturnLabel

R4 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

29.68%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

30.18%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

R5

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.08%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

100

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

312

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

542

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,201

Label

rr_AverageAnnualReturnLabel

R5 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

29.68%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

30.18%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 11, 2009

[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 Global Real Estate Fund

MFS Global Real Estate Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. The annual fund operating expenses for Class B, Class C, Class R1, Class R2, Class R3, and Class R4 shares are based on estimated “Other Expenses” for the current fiscal year expressed as a percentage of the fund’s estimated average net assets during the period.

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-13 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees MFS Global Real Estate Fund	A		B	C	I	R1	R2	R3	R4	R5
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	none	none	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	none	none	none	none	none

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

Annual Fund Operating Expenses MFS Global Real Estate Fund	A	B	C	I	R1	R2	R3	R4	R5
Management Fee	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses	0.08%	0.08%	0.08%	0.08%	0.08%	0.08%	0.08%	0.08%	0.08%
Total Annual Fund Operating Expenses	1.23%	1.98%	1.98%	0.98%	1.98%	1.48%	1.23%	0.98%	0.98%

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 Global Real Estate Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	693	943	1,212	1,978
B	601	921	1,268	2,113
C	301	621	1,068	2,306
I	100	312	542	1,201
R1	201	621	1,068	2,306
R2	151	468	808	1,768
R3	125	390	676	1,489
R4	100	312	542	1,201
R5	100	312	542	1,201

Expense Example No Redemption MFS Global Real Estate Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	201	621	1,068	2,113
C	201	621	1,068	2,306

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 46% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in U.S. and foreign real estate-related investments.

MFS normally invests the fund’s assets primarily in equity securities.

MFS generally focuses the fund’s investments in equity real estate investment trusts (“REITs”) as well as similar entities formed under the laws of non-U.S. countries, but may also invest in mortgage REITs, hybrid REITs and other U.S. and foreign real estate-related investments, including emerging market real estate-related investments.

MFS may invest the fund’s assets in real estate-related investments of any size.  However, issuers of real estate-related investments tend to be small-to-medium-sized.

MFS typically allocates the fund’s investments across various geographic areas, REIT managers and property types, but may from time to time focus the fund’s investments in any one or a few of these areas.

MFS may invest a large percentage of the fund’s assets in issuers in a single country, a small number of countries, or a particular geographic region.

MFS selects investments by analyzing the fundamental and relative values of potential investments.

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:

Real Estate-Related Investment Risk:  The fund’s performance will be closely tied to the performance of real estate-related investments and as a result, can be more volatile than the performance of more broadly-diversified funds. The risks of investing in real estate-related investments include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.

Small to Medium Cap Risk:  The securities of small and medium-sized real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Currency Risk:  The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, and other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency.

Geographic Concentration Risk: The fund’s performance could be closely tied to the market, currency, economic, political, regulatory, geopolitical, and other conditions in the countries or regions in which the fund invests and could be more volatile than the performance of more geographically-diversified funds.

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.

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 three-month period ended March 31, 2013 was 5.59%. During the period(s) shown in the bar chart, the highest quarterly return was 18.70% (for the calendar quarter ended September 30, 2010) and the lowest quarterly return was (18.05)% (for the calendar quarter ended September 30, 2011).

Performance Table.

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

Average Annual Returns MFS Global Real Estate Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, Life Inception	Average Annual Returns, Inception Date
B	B Shares Returns Before Taxes	24.40%	28.50%	Mar. 11, 2009
C	C Shares Returns Before Taxes	27.40%	28.89%	Mar. 11, 2009
I	I Shares Returns Before Taxes	29.68%	30.18%	Mar. 11, 2009
R1	R1 Shares Returns Before Taxes	28.40%	28.89%	Mar. 11, 2009
R2	R2 Shares Returns Before Taxes	29.04%	29.53%	Mar. 11, 2009
R3	R3 Shares Returns Before Taxes	29.36%	29.85%	Mar. 11, 2009
R4	R4 Shares Returns Before Taxes	29.68%	30.18%	Mar. 11, 2009
R5	R5 Shares Returns Before Taxes	29.68%	30.18%	Mar. 11, 2009
A	A Shares Returns Before Taxes	22.04%	27.87%	Mar. 11, 2009
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	19.76%	22.05%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	14.89%	21.04%
FTSE EPRA/NAREIT Developed Real Estate Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) FTSE EPRA/NAREIT Developed Real Estate Index	28.65%	32.27%	Mar. 11, 2009

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 Government Securities Fund

MFS Government Securities Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on current income, 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 MFS Government Securities Fund	A		B	C	I	R1	R2	R3	R4	R5
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none	none	none	none	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	none	none	none	none	none

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

Annual Fund Operating Expenses MFS Government Securities Fund	A	B	C	I	R1	R2	R3	R4	R5
Management Fee	0.40%	0.40%	0.40%	0.40%	0.40%	0.40%	0.40%	0.40%	0.40%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses	0.20%	0.20%	0.20%	0.20%	0.20%	0.20%	0.20%	0.20%	0.10%
Total Annual Fund Operating Expenses	0.85%	1.60%	1.60%	0.60%	1.60%	1.10%	0.85%	0.60%	0.50%

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 Government Securities Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	558	733	924	1,474
B	563	805	1,071	1,699
C	263	505	871	1,900
I	61	192	335	750
R1	163	505	871	1,900
R2	112	350	606	1,340
R3	87	271	471	1,049
R4	61	192	335	750
R5	51	160	280	628

Expense Example No Redemption MFS Government Securities Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	163	505	871	1,699
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 81% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in U.S. Government securities.

MFS generally invests substantially all of the fund’s assets in investment grade debt instruments.

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.

U.S. Government securities not supported as to the payment of principal or interest by the U.S. Treasury are subject to greater credit risk than are U.S. Government securities supported by the U.S. Treasury.

Issuer Focus Risk:  The fund’s performance could be more volatile than the performance of more diversified funds.

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.

Inflation-Adjusted Debt Instruments Risk:  Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

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 three-month period ended March 31, 2013 was (0.30)%. During the period(s) shown in the bar chart, the highest quarterly return was 5.29% (for the calendar quarter ended December 31, 2008) and the lowest quarterly return was (2.23)% (for the calendar quarter ended June 30, 2004).

Performance Table.

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

Average Annual Returns MFS Government Securities Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, 10 Years
B	B Shares Returns Before Taxes	(2.64%)	4.18%	3.80%
C	C Shares Returns Before Taxes	0.33%	4.49%	3.63%
I	I Shares Returns Before Taxes	2.34%	5.56%	4.68%
R1	R1 Shares Returns Before Taxes	1.32%	4.51%	3.55%
R2	R2 Shares Returns Before Taxes	1.83%	5.04%	4.05%
R3	R3 Shares Returns Before Taxes	2.08%	5.30%	4.33%
R4	R4 Shares Returns Before Taxes	2.34%	5.56%	4.62%
R5	R5 Shares Returns Before Taxes	2.27%	5.54%	4.68%
A	A Shares Returns Before Taxes	(2.76%)	4.28%	3.90%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(3.71%)	3.03%	2.51%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	(1.73%)	2.92%	2.50%
Barclays U.S. Government/Mortgage Bond Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Government/Mortgage Bond Index	2.27%	5.46%	4.87%

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 New Discovery Value Fund

MFS New Discovery Value Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek 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. Expenses have been adjusted to reflect current fee arrangements.

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-15 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees MFS New Discovery Value Fund	A		B	C	I	R1	R2	R3	R4	R5
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	none	none	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	none	none	none	none	none

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 Discovery Value Fund		A	B	C	I	R1	R2	R3	R4	R5
Management Fee		0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%	0.90%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses		0.47%	0.47%	0.47%	0.47%	0.47%	0.47%	0.47%	0.47%	0.41%
Total Annual Fund Operating Expenses		1.62%	2.37%	2.37%	1.37%	2.37%	1.87%	1.62%	1.37%	1.31%
Fee Reductions and/or Expense Reimbursements	[1]	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.17%)	(0.15%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.45%	2.20%	2.20%	1.20%	2.20%	1.70%	1.45%	1.20%	1.16%

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 Discovery Value Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	714	1,025	1,375	2,359
B	623	1,006	1,434	2,492
C	323	706	1,234	2,679
I	122	400	717	1,616
R1	223	706	1,234	2,679
R2	173	554	979	2,162
R3	148	477	848	1,892
R4	122	400	717	1,616
R5	118	385	689	1,552

Expense Example No Redemption MFS New Discovery Value Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
B	223	706	1,234	2,492
C	223	706	1,234	2,679

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 67% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, equity interests in real estate investment trusts (REITs), and depositary receipts for such securities.

MFS focuses on investing the fund’s assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).

While MFS may invest the fund’s assets in companies of any size, MFS generally focuses on companies with small capitalizations.

MFS may invest the fund’s assets in foreign securities.

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 issuers. Quantitative models that systematically evaluate issuers may also be considered.

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:

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Value Company Risk:  The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Small Cap Risk:  The stocks of small cap companies can be more volatile than stocks of larger companies.

Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

Real Estate Investment Trust Risk: The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

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.

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 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 three-month period ended March 31, 2013 was 12.70%. During the period(s) shown in the bar chart, the highest quarterly return was 14.86% (for the calendar quarter ended March 31, 2012) and the lowest quarterly return was (2.76)% (for the calendar quarter ended June 30, 2012).

Performance Table.

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

Average Annual Returns MFS New Discovery Value Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, Life Inception	Average Annual Returns, Inception Date
B	B Shares Returns Before Taxes	15.19%	3.67%	May 26, 2011
C	C Shares Returns Before Taxes	18.29%	6.11%	May 26, 2011
I	I Shares Returns Before Taxes	20.49%	7.17%	May 26, 2011
R1	R1 Shares Returns Before Taxes	19.21%	6.11%	May 26, 2011
R2	R2 Shares Returns Before Taxes	19.94%	6.66%	May 26, 2011
R3	R3 Shares Returns Before Taxes	20.21%	6.91%	May 26, 2011
R4	R4 Shares Returns Before Taxes	20.49%	7.17%	May 26, 2011
R5	R5 Shares Returns Before Taxes	20.51%	7.18%	May 26, 2011
A	A Shares Returns Before Taxes	13.24%	3.05%	May 26, 2011
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	11.05%	1.76%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	8.80%	1.92%
Russell 2000 Value Index	Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Value Index	18.05%	5.12%	May 26, 2011

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 1.45% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 2.20% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 1.20% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.70% of the fund's average daily net assets annually for Class R2 shares, and 1.16% of the fund's average daily net assets annually for Class R5 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least June 30, 2015.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Prospectus Date	rr_ProspectusDate	Jun. 28, 2013

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MFS Government Securities 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 current income, 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)

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 81% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

81.00%

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

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in U.S. Government securities.

MFS generally invests substantially all of the fund’s assets in investment grade debt instruments.

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.

U.S. Government securities not supported as to the payment of principal or interest by the U.S. Treasury are subject to greater credit risk than are U.S. Government securities supported by the U.S. Treasury.

Issuer Focus Risk:  The fund’s performance could be more volatile than the performance of more diversified funds.

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.

Inflation-Adjusted Debt Instruments Risk:  Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

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 three-month period ended March 31, 2013 was (0.30)%. During the period(s) shown in the bar chart, the highest quarterly return was 5.29% (for the calendar quarter ended December 31, 2008) and the lowest quarterly return was (2.23)% (for the calendar quarter ended June 30, 2004).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the three-month period

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(0.30%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2008

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.29%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2004

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.23%)

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 U.S. Government/Mortgage Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Government/Mortgage Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.27%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.46%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.87%

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

0.20%

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

1.54%

Annual Return 2004

rr_AnnualReturn2004

3.30%

Annual Return 2005

rr_AnnualReturn2005

2.17%

Annual Return 2006

rr_AnnualReturn2006

3.60%

Annual Return 2007

rr_AnnualReturn2007

7.07%

Annual Return 2008

rr_AnnualReturn2008

8.51%

Annual Return 2009

rr_AnnualReturn2009

4.23%

Annual Return 2010

rr_AnnualReturn2010

4.59%

Annual Return 2011

rr_AnnualReturn2011

7.19%

Annual Return 2012

rr_AnnualReturn2012

2.08%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

(2.76%)

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.28%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.90%

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

(3.71%)

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

3.03%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

2.51%

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

(1.73%)

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

2.92%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

2.50%

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

0.20%

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

(2.64%)

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.18%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.80%

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

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

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

0.33%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.49%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.63%

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

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

61

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

192

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

335

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

750

Label

rr_AverageAnnualReturnLabel

I Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.34%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.56%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.68%

R1

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

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

163

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

Label

rr_AverageAnnualReturnLabel

R1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.32%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.51%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

3.55%

R2

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

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.10%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

112

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

350

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

606

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,340

Label

rr_AverageAnnualReturnLabel

R2 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

1.83%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.04%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.05%

R3

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

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.85%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

87

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

271

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

471

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,049

Label

rr_AverageAnnualReturnLabel

R3 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.08%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.30%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.33%

R4

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

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

61

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

192

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

335

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

750

Label

rr_AverageAnnualReturnLabel

R4 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.34%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.56%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.62%

R5

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

0.10%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.50%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

51

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

160

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

280

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 628

Label

rr_AverageAnnualReturnLabel

R5 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.27%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.54%

Average Annual Returns, 10 Years

rr_AverageAnnualReturnYear10

4.68%

[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 Diversified 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 current income, 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. Expenses have been adjusted to reflect the estimated expenses of investing in another MFS 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 11 of the fund’s prospectus and “Waivers of Sales Charges” on page I-15 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 64% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

64.00%

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

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in a broad range of debt instruments and equity securities of U.S. and foreign issuers, including convertible securities, real estate-related investments, and emerging market securities. MFS may invest the fund’s assets in other mutual funds advised by MFS that invest in such instruments and securities instead of investing directly in such instruments and securities.

MFS allocates the fund’s assets across these categories based on its interpretation of economic and money market conditions, fiscal and monetary policy and asset class and/or security values. These allocations may vary from time to time.

MFS focuses the fund’s debt investments on U.S. Government securities, less than investment grade quality debt instruments (lower quality debt instruments), and debt instruments of emerging market issuers. Of the fund’s investments in debt instruments, MFS may invest up to 100% of these investments directly or indirectly in lower quality debt instruments.

For the equity portion of the fund, MFS focuses on investing the fund’s assets in dividend-paying stocks and/or in the stocks of companies it believes are undervalued compared to their perceived worth (value companies). While MFS may invest the equity portion of the fund’s assets in companies of any size, MFS generally focuses on companies with large capitalizations.

For the real estate-related portion of the fund, MFS invests the fund’s assets in real estate investment trusts (REITs) and other companies principally engaged in the real estate industry. MFS generally focuses the fund’s investments in equity REITs, but may also invest in mortgage REITs and other real estate-related investments.  Issuers of real estate-related investments tend to be small- to medium-sized.

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 or currency 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 based on fundamental analysis of individual issuers and instruments and quantitative models that systematically evaluate issuers and instruments. 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:

Investment Selection and Allocation Risk: MFS’ investment analysis, its selection of investments, and its assessment of the risk/return potential of asset classes 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.

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.

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.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Currency Risk:  The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, and other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency.

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.

Inflation-Adjusted Debt Instruments Risk:  Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

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.

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Value Company Risk:  The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Real Estate-Related Investment Risk: The risks of investing in real estate-related securities include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

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.

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 and one or more other measures of performance for markets in which the fund may invest.

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 and one or more other measures of performance for markets in which the fund may invest.

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 three-month period ended March 31, 2013 was 4.04%. During the period(s) shown in the bar chart, the highest quarterly return was 15.83% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (15.17)% (for the calendar quarter ended December 31, 2008).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the three-month period

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

4.04%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.83%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(15.17%)

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)

Standard & Poor’s 500 Stock Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

16.00%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

1.66%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

3.94%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

Barclays U.S. Government/Mortgage Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Government/Mortgage Bond Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

2.27%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.46%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.05%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

15.78%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

10.45%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

9.37%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

JPMorgan Emerging Markets Bond Index Global

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) JPMorgan Emerging Markets Bond Index Global

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

18.54%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

10.47%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

10.46%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

MSCI U.S. REIT Index (gross div)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI U.S. REIT Index (gross div)

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

17.77%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

5.58%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

4.97%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

Russell 1000 Value Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparisons (Reflects no deduction for fees, expenses or taxes) Russell 1000 Value Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

17.51%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

0.59%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

2.66%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.09%

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

581

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

805

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,047

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,741

Annual Return 2007

rr_AnnualReturn2007

0.79%

Annual Return 2008

rr_AnnualReturn2008

(20.41%)

Annual Return 2009

rr_AnnualReturn2009

30.26%

Annual Return 2010

rr_AnnualReturn2010

13.92%

Annual Return 2011

rr_AnnualReturn2011

5.13%

Annual Return 2012

rr_AnnualReturn2012

13.19%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

7.81%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

6.01%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.31%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

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

6.72%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.53%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

4.76%

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

5.21%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

4.28%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

4.51%

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.84%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

287

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

579

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

996

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,159

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

187

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

579

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

996

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,159

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

11.46%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

6.28%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.33%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.84%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

86

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

268

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

466

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,037

Label

rr_AverageAnnualReturnLabel

I Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.47%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

7.32%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.39%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

R1

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.84%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

187

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

579

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

996

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,159

Label

rr_AverageAnnualReturnLabel

R1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

12.36%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

6.29%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.35%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

R2

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.34%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

136

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

425

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

734

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,613

Label

rr_AverageAnnualReturnLabel

R2 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.02%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

6.83%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.89%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

R3

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.09%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

111

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

347

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

601

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,329

Label

rr_AverageAnnualReturnLabel

R3 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.29%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

7.10%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.15%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

R4

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.18%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.84%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

86

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

268

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

466

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,037

Label

rr_AverageAnnualReturnLabel

R4 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.47%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

7.34%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.40%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

R5

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

0.65%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.10%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.76%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

78

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

243

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

422

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 942

Label

rr_AverageAnnualReturnLabel

R5 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.47%

Average Annual Returns, 5 Years

rr_AverageAnnualReturnYear05

7.32%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.39%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2006

[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 Diversified Income Fund

MFS Diversified Income Fund Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on current income, 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. Expenses have been adjusted to reflect the estimated expenses of investing in another MFS 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 11 of the fund’s prospectus and “Waivers of Sales Charges” on page I-15 of the fund’s statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees MFS Diversified Income Fund	A		C	I	R1	R2	R3	R4	R5
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.75%		none	none	none	none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less)	1.00%	[1]	1.00%	none	none	none	none	none	none

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

Annual Fund Operating Expenses MFS Diversified Income Fund	A	C	I	R1	R2	R3	R4	R5
Management Fee	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%	0.65%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses	0.18%	0.18%	0.18%	0.18%	0.18%	0.18%	0.18%	0.10%
Acquired Fund Fees and Expenses	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%
Total Annual Fund Operating Expenses	1.09%	1.84%	0.84%	1.84%	1.34%	1.09%	0.84%	0.76%

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 Diversified Income Fund (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
A	581	805	1,047	1,741
C	287	579	996	2,159
I	86	268	466	1,037
R1	187	579	996	2,159
R2	136	425	734	1,613
R3	111	347	601	1,329
R4	86	268	466	1,037
R5	78	243	422	942

Expense Example No Redemption (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
MFS Diversified Income Fund C	187	579	996	2,159

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 64% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in a broad range of debt instruments and equity securities of U.S. and foreign issuers, including convertible securities, real estate-related investments, and emerging market securities. MFS may invest the fund’s assets in other mutual funds advised by MFS that invest in such instruments and securities instead of investing directly in such instruments and securities.

MFS allocates the fund’s assets across these categories based on its interpretation of economic and money market conditions, fiscal and monetary policy and asset class and/or security values. These allocations may vary from time to time.

MFS focuses the fund’s debt investments on U.S. Government securities, less than investment grade quality debt instruments (lower quality debt instruments), and debt instruments of emerging market issuers. Of the fund’s investments in debt instruments, MFS may invest up to 100% of these investments directly or indirectly in lower quality debt instruments.

For the equity portion of the fund, MFS focuses on investing the fund’s assets in dividend-paying stocks and/or in the stocks of companies it believes are undervalued compared to their perceived worth (value companies). While MFS may invest the equity portion of the fund’s assets in companies of any size, MFS generally focuses on companies with large capitalizations.

For the real estate-related portion of the fund, MFS invests the fund’s assets in real estate investment trusts (REITs) and other companies principally engaged in the real estate industry. MFS generally focuses the fund’s investments in equity REITs, but may also invest in mortgage REITs and other real estate-related investments.  Issuers of real estate-related investments tend to be small- to medium-sized.

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 or currency 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 based on fundamental analysis of individual issuers and instruments and quantitative models that systematically evaluate issuers and instruments. 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:

Investment Selection and Allocation Risk: MFS’ investment analysis, its selection of investments, and its assessment of the risk/return potential of asset classes 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.

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.

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.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Currency Risk:  The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, and other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency.

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.

Inflation-Adjusted Debt Instruments Risk:  Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

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.

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Value Company Risk:  The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Real Estate-Related Investment Risk: The risks of investing in real estate-related securities include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

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.

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 and one or more other measures of performance for markets in which the fund may invest.

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 three-month period ended March 31, 2013 was 4.04%. During the period(s) shown in the bar chart, the highest quarterly return was 15.83% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (15.17)% (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 Diversified Income Fund	Label	Average Annual Returns, 1 Year	Average Annual Returns, 5 Years	Average Annual Returns, Life Inception	Average Annual Returns, Inception Date
C	C Shares Returns Before Taxes	11.46%	6.28%	6.33%	May 26, 2006
I	I Shares Returns Before Taxes	13.47%	7.32%	7.39%	May 26, 2006
R1	R1 Shares Returns Before Taxes	12.36%	6.29%	6.35%	May 26, 2006
R2	R2 Shares Returns Before Taxes	13.02%	6.83%	6.89%	May 26, 2006
R3	R3 Shares Returns Before Taxes	13.29%	7.10%	7.15%	May 26, 2006
R4	R4 Shares Returns Before Taxes	13.47%	7.34%	7.40%	May 26, 2006
R5	R5 Shares Returns Before Taxes	13.47%	7.32%	7.39%	May 26, 2006
A	A Shares Returns Before Taxes	7.81%	6.01%	6.31%	May 26, 2006
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	6.72%	4.53%	4.76%
After Taxes on Distributions and Sale of Fund Shares A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	5.21%	4.28%	4.51%
Standard & Poor’s 500 Stock Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index	16.00%	1.66%	3.94%	May 26, 2006
Barclays U.S. Government/Mortgage Bond Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Government/Mortgage Bond Index	2.27%	5.46%	6.05%	May 26, 2006
Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index	15.78%	10.45%	9.37%	May 26, 2006
JPMorgan Emerging Markets Bond Index Global	Index Comparisons (Reflects no deduction for fees, expenses or taxes) JPMorgan Emerging Markets Bond Index Global	18.54%	10.47%	10.46%	May 26, 2006
MSCI U.S. REIT Index (gross div)	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI U.S. REIT Index (gross div)	17.77%	5.58%	4.97%	May 26, 2006
Russell 1000 Value Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Russell 1000 Value Index	17.51%	0.59%	2.66%	May 26, 2006

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 New Discovery Value 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 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. Expenses have been adjusted to reflect current fee arrangements.

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-15 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

2015-06-30

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 67% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

67.00%

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

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Expenses have been adjusted to reflect current fee arrangements.

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

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, equity interests in real estate investment trusts (REITs), and depositary receipts for such securities.

MFS focuses on investing the fund’s assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).

While MFS may invest the fund’s assets in companies of any size, MFS generally focuses on companies with small capitalizations.

MFS may invest the fund’s assets in foreign securities.

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 issuers. Quantitative models that systematically evaluate issuers may also be considered.

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:

Stock Market/Company Risk:  Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Value Company Risk:  The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general.

Small Cap Risk:  The stocks of small cap companies can be more volatile than stocks of larger companies.

Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

Real Estate Investment Trust Risk: The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

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.

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 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 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 three-month period ended March 31, 2013 was 12.70%. During the period(s) shown in the bar chart, the highest quarterly return was 14.86% (for the calendar quarter ended March 31, 2012) and the lowest quarterly return was (2.76)% (for the calendar quarter ended June 30, 2012).

Year to Date Return, Label

rr_YearToDateReturnLabel

The total return for the three-month period

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

12.70%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

highest quarterly return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.86%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest quarterly return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.76%)

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)

Russell 2000 Value Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Value Index

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

18.05%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

5.12%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

A

Risk/Return:

rr_RiskReturnAbstract

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.62%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

1.45%

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

714

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,025

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,375

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,359

Annual Return 2012

rr_AnnualReturn2012

20.15%

Label

rr_AverageAnnualReturnLabel

A Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

13.24%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

3.05%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

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

11.05%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

1.76%

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

8.80%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

1.92%

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.37%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

2.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

623

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,006

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,434

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,492

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

223

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

706

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,234

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,492

Label

rr_AverageAnnualReturnLabel

B Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

15.19%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

3.67%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.37%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

2.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

323

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

706

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,234

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,679

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

223

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

706

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,234

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,679

Label

rr_AverageAnnualReturnLabel

C Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

18.29%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.11%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.37%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

1.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

122

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

400

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

717

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,616

Label

rr_AverageAnnualReturnLabel

I Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

20.49%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.17%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

R1

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.37%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

2.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

223

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

706

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,234

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,679

Label

rr_AverageAnnualReturnLabel

R1 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

19.21%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.11%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

R2

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.87%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[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

173

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

554

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

979

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,162

Label

rr_AverageAnnualReturnLabel

R2 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

19.94%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.66%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

R3

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.62%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

1.45%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

148

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

477

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

848

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,892

Label

rr_AverageAnnualReturnLabel

R3 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

20.21%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

6.91%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

R4

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.47%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.37%

Fee Reductions and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.17%)

^[2]

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

rr_NetExpensesOverAssets

1.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

122

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

400

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

717

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,616

Label

rr_AverageAnnualReturnLabel

R4 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

20.49%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.17%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

R5

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

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.31%

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

1.16%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

118

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

385

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

689

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,552

Label

rr_AverageAnnualReturnLabel

R5 Shares Returns Before Taxes

Average Annual Returns, 1 Year

rr_AverageAnnualReturnYear01

20.51%

Average Annual Returns, Life Inception

rr_AverageAnnualReturnSinceInception

7.18%

Average Annual Returns, Inception Date

rr_AverageAnnualReturnInceptionDate

May 26, 2011

[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 1.45% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 2.20% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 1.20% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.70% of the fund's average daily net assets annually for Class R2 shares, and 1.16% of the fund's average daily net assets annually for Class R5 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least June 30, 2015.

XML

Document and Entity Information	0 Months Ended
	Feb. 28, 2013
Risk/Return:
Document Type	485BPOS
Document Period End Date	Feb. 28, 2013
Registrant Name	MFS SERIES TRUST XIII
Central Index Key	0000356349
Amendment Flag	false
Document Creation Date	Jun. 27, 2013
Document Effective Date	Jun. 28, 2013
Prospectus Date	Jun. 28, 2013
MFS Diversified Income Fund | A
Risk/Return:
Trading Symbol	DIFAX
MFS Diversified Income Fund | C
Risk/Return:
Trading Symbol	DIFCX
MFS Diversified Income Fund | I
Risk/Return:
Trading Symbol	DIFIX
MFS Diversified Income Fund | R1
Risk/Return:
Trading Symbol	DIFDX
MFS Diversified Income Fund | R2
Risk/Return:
Trading Symbol	DIFEX
MFS Diversified Income Fund | R3
Risk/Return:
Trading Symbol	DIFFX
MFS Diversified Income Fund | R4
Risk/Return:
Trading Symbol	DIFGX
MFS Diversified Income Fund | R5
Risk/Return:
Trading Symbol	DIFHX
MFS Global Real Estate Fund | A
Risk/Return:
Trading Symbol	MGLAX
MFS Global Real Estate Fund | I
Risk/Return:
Trading Symbol	MGLIX
MFS Global Real Estate Fund | R5
Risk/Return:
Trading Symbol	MGLRX
MFS Government Securities Fund | I
Risk/Return:
Trading Symbol	MGSIX
MFS Government Securities Fund | A
Risk/Return:
Trading Symbol	MFGSX
MFS Government Securities Fund | R4
Risk/Return:
Trading Symbol	MFGJX
MFS Government Securities Fund | B
Risk/Return:
Trading Symbol	MFGBX
MFS Government Securities Fund | C
Risk/Return:
Trading Symbol	MFGDX
MFS Government Securities Fund | R1
Risk/Return:
Trading Symbol	MFGGX
MFS Government Securities Fund | R2
Risk/Return:
Trading Symbol	MGVSX
MFS Government Securities Fund | R3
Risk/Return:
Trading Symbol	MFGHX
MFS Government Securities Fund | R5
Risk/Return:
Trading Symbol	MFGKX
MFS New Discovery Value Fund | A
Risk/Return:
Trading Symbol	NDVAX
MFS New Discovery Value Fund | B
Risk/Return:
Trading Symbol	NDVBX
MFS New Discovery Value Fund | C
Risk/Return:
Trading Symbol	NDVCX
MFS New Discovery Value Fund | I
Risk/Return:
Trading Symbol	NDVIX
MFS New Discovery Value Fund | R1
Risk/Return:
Trading Symbol	NDVRX
MFS New Discovery Value Fund | R2
Risk/Return:
Trading Symbol	NDVSX
MFS New Discovery Value Fund | R3
Risk/Return:
Trading Symbol	NDVTX
MFS New Discovery Value Fund | R4
Risk/Return:
Trading Symbol	NDVUX
MFS New Discovery Value Fund | R5
Risk/Return:
Trading Symbol	NDVVX