485BPOS

As filed with the Securities and Exchange Commission on October 19, 2012

1933 Act File No. 33-1657

1940 Act File No. 811-4492

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C.  20549

FORM N-1A

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 88

AND

REGISTRATION STATEMENT

UNDER THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 87

MFS® SERIES TRUST X

(Exact Name of Registrant as Specified in Charter)

500 Boylston Street, Boston, Massachusetts 02116

(Address of Principal Executive Offices)

Registrant’s Telephone Number, including Area Code:  617-954-5000

Susan S. Newton Massachusetts Financial Services Company,

500 Boylston Street, Boston, MA  02116

(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 October, 2012

MFS® SERIES TRUST X
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 October 19, 2012.

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

WILLIAM R. GUTOW*	Trustee
William R. Gutow
MICHAEL HEGARTY*	Trustee
Michael Hegarty
JOHN P. KAVANAUGH*	Trustee
John P. Kavanaugh
ROBERT J. MANNING*	Trustee
Robert J. Manning
J. DALE SHERRATT*	Trustee
J. Dale Sherratt
LAURIE J. THOMSEN*	Trustee
Laurie J. Thomsen
ROBERT W. UEK*	Trustee
Robert W. Uek
		*By:	SUSAN S. NEWTON
		Name:	Susan S. Newton
			as Attorney-in-fact
		Executed by Susan S. Newton on behalf of those indicated pursuant to a Power of Attorney, dated September 11, 2012 (Trustees), and a Power of Attorney, dated September 11, 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 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 11th day of September, 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 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 11th day of September, 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 X

MFS® ABSOLUTE RETURN FUND

MFS® AGGRESSIVE GROWTH ALLOCATION FUND

MFS® CONSERVATIVE ALLOCATION FUND

MFS® EMERGING MARKETS EQUITY FUND

MFS® GLOBAL BOND FUND

MFS® GROWTH ALLOCATION FUND

MFS® INTERNATIONAL DIVERSIFICATION FUND

MFS® INTERNATIONAL GROWTH FUND

MFS® INTERNATIONAL VALUE FUND

MFS® MODERATE ALLOCATION 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 [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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. Expenses for Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect current fee arrangements. The annual fund operating expenses for Class R5 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 11 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 10% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	10.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The annual fund operating expenses for Class R5 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.
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	In managing the fund, MFS (Massachusetts Financial Services Company, the fund's investment adviser) employs an absolute return investment approach, which means the fund seeks to earn a positive return regardless of market conditions. As a result, if this strategy is successful, it is expected that the fund will outperform the general equity market during periods of flat or negative market performance, will underperform during periods of strong positive market performance, and will typically produce less volatile returns than the general equity market.    MFS seeks to achieve the fund's objective by generating returns from a combination of (1) individual security selection of primarily debt instruments and (2) a tactical asset allocation overlay primarily using derivative instruments to manage the fund's exposure to asset classes, markets and currencies. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps. The fund's performance may not be correlated with the performance of the asset classes, markets or currencies represented by the individual investments selected by MFS.    Individual Security Selection:  In selecting direct investments for the fund, MFS normally invests the fund's assets primarily in debt instruments.    Debt instruments include corporate bonds, U.S. Government securities, asset-backed securities, municipal instruments, foreign government securities, inflation-adjusted bonds, and other obligations to repay money borrowed.    Of the fund's investments in debt instruments, MFS generally invests substantially all of these investments in investment grade debt instruments.    While MFS may invest the fund's assets in debt instruments of any effective maturity, MFS generally focuses on short and intermediate term debt instruments.    MFS may invest the fund's assets in U.S. and foreign securities, including emerging market securities.    While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives as part of its individual security selection process, 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. 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.    Tactical Asset Allocation Overlay:  MFS employs a top-down tactical asset allocation process to adjust the fund's exposure to asset classes, markets and currencies based on its assessment of the relative attractiveness of such asset classes, markets and currencies. MFS manages the fund's exposure to asset classes, markets and currencies primarily through the use of derivative instruments based on its proprietary quantitative models.    In managing the tactical overlay, MFS may increase or decrease the fund's exposure to asset classes, markets and/or currencies resulting from MFS' individual security selection based on MFS' assessment of the risk/return potential of such asset classes, markets and/or currencies. MFS may also expose the fund to asset classes, markets and/or currencies in which its individual security selection has resulted in no or little exposure (e.g., commodity-related investments, real estate-related investments, equity securities, inflation-adjusted debt instruments). After taking into account the tactical overlay, the fund's exposure to certain asset classes in which its individual security selection has resulted in no or little exposure will normally fall within the following ranges:    Asset Class                           Range   U.S. and foreign equity securities      ±15% Inflation-adjusted debt instruments     ±10% Commodity-related investments           ±10% Real estate-related investments         ± 5%    After taking into account the tactical overlay, the fund's exposure to the less than investment grade quality debt instrument (lower quality debt instrument) and long term debt instrument asset classes may at times be significant, and the fund may have significant exposure to issuers in a single country, a small number of countries, or a particular geographic region. MFS may adjust the fund's net exposure to asset classes, markets and/or currencies by taking net short positions in an asset class, market or currency if MFS believes the risk/return potential of such asset class, market or currency is unattractive.  Alternatively, MFS may cause the fund to take net long positions in an asset class, market or currency if MFS believes such asset class, market or currency appears attractive. MFS may also use derivatives to seek to limit the fund's exposure to certain extreme market events.    MFS' tactical allocation process for the fund will typically make extensive use of derivatives.
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, its assessment of the risk/return potential of asset classes, markets and currencies, and its adjustments to the fund's exposure to asset classes, markets, and currencies through the use of derivatives 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.    Investment Strategy Risk:  The fund's strategy to manage its exposure to asset classes, markets, and currencies may not produce the intended results. In addition, the strategies MFS may implement to limit the fund's exposure to certain extreme market events may not work as intended, and the costs associated with such strategies will reduce the fund's returns. 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, or 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.    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.    Foreign and Emerging Markets Risk: Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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, or 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. 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.    Commodity Risk:  The value of commodities may be more volatile than the value of equity securities or debt instruments and their value may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The price of a commodity may be affected by demand/supply imbalances in the market for the commodity.    Tax Risk:  In order to qualify as a regulated investment company (RIC) under the Internal Revenue Code of 1986, as amended, the fund must meet certain requirements regarding the source of its income, the diversification of its assets, and the distribution of its income. If the fund were to fail to qualify as a RIC and became subject to federal income tax, shareholders of the fund would be subject to the risk of diminished returns.    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; property tax rates, 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. 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 are not included because the fund has not had a full calendar year of operations.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The bar chart and performance table are not included because the fund has not had a full calendar year of operations.
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.54%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.14%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	586
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	901
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,239
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,190
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	592
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	977
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,389
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,406
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	192
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	677
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,189
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,406
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	292
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	677
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,189
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,595
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	192
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	677
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,189
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,595
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	91
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	369
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	669
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,521
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	192
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	677
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,189
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,595
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.79%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.39%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	142
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	524
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	932
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,072
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.54%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.14%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	116
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	447
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	802
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,801
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	91
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	369
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	669
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,521
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R5
Management Fee	rr_ManagementFeesOverAssets	0.65%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.29%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.40%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	91
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	369
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	669
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,521

[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 1.15% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 1.90% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.90% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.40% of the fund's average daily net assets annually for Class R2 shares, and 0.89% 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 September 30, 2013.

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MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond 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 for Class A, Class B, Class C, Class I,
Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect
current fee arrangements. The annual fund operating expenses for Class R5 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 9 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 Global Bond Fund	A		B	C	I	R1	R2	R3	R4	R5
Shareholder Fees Column [Text]	A		B	C	I	ALL R	ALL R	ALL R	ALL R	ALL R
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 Global Bond Fund		A	B	C	I	R1	R2	R3	R4	R5
Operating Expenses Column [Text]		A	B	C	I	R1	R2	R3	R4	R5
Management Fee		0.60%	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses		0.25%	0.25%	0.25%	0.25%	0.25%	0.25%	0.25%	0.25%	0.25%
Total Annual Fund Operating Expenses		1.10%	1.85%	1.85%	0.85%	1.85%	1.35%	1.10%	0.85%	0.85%
Fee Reductions and/or Expense Reimbursements	[1]	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.09%	1.84%	1.84%	0.84%	1.84%	1.34%	1.09%	0.84%	0.84%

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 Bond Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	581	807	1,051	1,751
B	Class B Shares assuming redemption at end of period	587	881	1,200	1,972
C	Class C Shares assuming redemption at end of period	287	581	1,000	2,168
I	Class I Shares	86	270	470	1,048
R1	Class R1 Shares	187	581	1,000	2,168
R2	Class R2 Shares	136	427	738	1,623
R3	Class R3 Shares	111	349	605	1,339
R4	Class R4 Shares	86	270	470	1,048
R5	Class R5 Shares	86	270	470	1,048

Expense Example, No Redemption MFS Global Bond Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	187	581	1,000	1,972
C	Class C Shares assuming no redemption at end of period	187	581	1,000	2,168

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 98% 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 debt instruments of
U.S. and foreign issuers, including emerging markets issuers.
  
While MFS may invest the fund's assets in debt instruments of any type, MFS
generally focuses on debt instruments of U.S. and foreign governments.
  
MFS may invest up to 100% of the fund's assets in less than investment grade
quality debt instruments (lower quality debt instruments).

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 may invest up to 35% of the fund's assets in any industry that accounts for
more than 20% of the global bond market.

The fund is a non-diversified fund. This means that MFS may invest a relatively
large percentage of the fund's assets in a single issuer or a small number of
issuers.
  
While MFS may use derivatives for any investment purpose, to the extent MFS uses
derivatives, MFS expects to use derivatives primarily to increase or decrease
exposure to a particular market, segment of the market, or security, to increase
or decrease interest rate or currency exposure, or as alternatives to direct
investments. Derivatives include futures, forward contracts, options, structured
securities, inverse floating rate instruments, and swaps.
  
MFS generally uses a top-down approach to buying and selling investments for the
fund. MFS allocates the fund's assets across countries and selects investments
primarily based on fundamental economic and financial analysis. Quantitative
models that systematically evaluate economic and financial factors may also be
considered. MFS may also use a bottom-up investment approach, particularly for
corporate debt instruments, selecting investments based on fundamental analysis
of individual instruments and their issuers.

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, or 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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.

Geographic Concentration Risk:  The fund's performance could be closely tied to
the market, currency, economic, political, regulatory, geopolitical, or 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.
  
Non-Diversification Risk:  Because MFS may invest a relatively large percentage
of the fund's assets in a single issuer or small number of issuers, the fund's
performance could be closely tied to the value of that one issuer or issuers,
and could be more volatile than the performance of diversified funds.

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.
  
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.
  
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.
  
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.

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 six-month period ended June 30, 2012 was 0.53%. During
the period(s) shown in the bar chart, the highest quarterly return was 3.87%
(for the calendar quarter ended June 30, 2011) and the lowest quarterly return
was (0.07)% (for the calendar quarter ended March 31, 2011).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Global Bond Fund	Label	1 Year	Since Inception	Inception Date
A	A Shares Returns Before Taxes	0.97%	5.14%	Jun. 02, 2010
B	B Shares Returns Before Taxes	0.78%	4.78%	Jun. 02, 2010
C	C Shares Returns Before Taxes	3.85%	7.22%	Jun. 02, 2010
I	I Shares Returns Before Taxes	5.68%	8.29%	Jun. 02, 2010
R1	R1 Shares Returns Before Taxes	4.74%	7.22%	Jun. 02, 2010
R2	R2 Shares Returns Before Taxes	5.16%	7.73%	Jun. 02, 2010
R3	R3 Shares Returns Before Taxes	5.42%	7.98%	Jun. 02, 2010
R4	R4 Shares Returns Before Taxes	5.79%	8.30%	Jun. 02, 2010
R5	R5 Shares Returns Before Taxes	5.68%	8.29%	Jun. 02, 2010
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(1.15%)	3.32%	Jun. 02, 2010
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	0.66%	3.35%	Jun. 02, 2010
JPMorgan Global Government Bond Index (Unhedged)	Index Comparison (Reflects no deduction for fees, expenses or taxes) JPMorgan Global Government Bond Index (Unhedged)	7.22%	9.81%	Jun. 02, 2010

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 1.10% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 1.85% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.85% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.35% of the fund's average daily net assets annually for Class R2 shares, and 0.84% 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 September 30, 2013.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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 for Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect current fee arrangements. The annual fund operating expenses for Class R5 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 9 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 98% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	98.00%
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
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The annual fund operating expenses for Class R5 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.
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 debt instruments of U.S. and foreign issuers, including emerging markets issuers.    While MFS may invest the fund's assets in debt instruments of any type, MFS generally focuses on debt instruments of U.S. and foreign governments.    MFS may invest up to 100% of the fund's assets in less than investment grade quality debt instruments (lower quality debt instruments). 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 may invest up to 35% of the fund's assets in any industry that accounts for more than 20% of the global bond market. The fund is a non-diversified fund. This means that MFS may invest a relatively large percentage of the fund's assets in a single issuer or a small number of issuers.    While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.    MFS generally uses a top-down approach to buying and selling investments for the fund. MFS allocates the fund's assets across countries and selects investments primarily based on fundamental economic and financial analysis. Quantitative models that systematically evaluate economic and financial factors may also be considered. MFS may also use a bottom-up investment approach, particularly for corporate debt instruments, selecting investments based on fundamental analysis of individual instruments and their issuers.
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, or 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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. Geographic Concentration Risk:  The fund's performance could be closely tied to the market, currency, economic, political, regulatory, geopolitical, or 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.    Non-Diversification Risk:  Because MFS may invest a relatively large percentage of the fund's assets in a single issuer or small number of issuers, the fund's performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds. 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.    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.    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.    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.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Because MFS may invest a relatively large percentage of the fund's assets in a single issuer or small number of issuers, the fund's performance could be closely tied to the value of that one issuer or issuers, and could be more volatile than the performance of diversified funds.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing 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 six-month period ended June 30, 2012 was 0.53%. During the period(s) shown in the bar chart, the highest quarterly return was 3.87% (for the calendar quarter ended June 30, 2011) and the lowest quarterly return was (0.07)% (for the calendar quarter ended March 31, 2011).
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, 2011)
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | JPMorgan Global Government Bond Index (Unhedged)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparison (Reflects no deduction for fees, expenses or taxes) JPMorgan Global Government Bond Index (Unhedged)
1 Year	rr_AverageAnnualReturnYear01	7.22%
Since Inception	rr_AverageAnnualReturnSinceInception	9.81%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.09%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	581
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	807
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,051
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,751
Annual Return 2011	rr_AnnualReturn2011	6.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.53%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.87%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	the lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.07%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	0.97%
Since Inception	rr_AverageAnnualReturnSinceInception	5.14%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(1.15%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.32%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	0.66%
Since Inception	rr_AverageAnnualReturnSinceInception	3.35%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	587
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	881
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,200
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,972
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	187
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	581
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,000
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,972
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	0.78%
Since Inception	rr_AverageAnnualReturnSinceInception	4.78%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	287
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	581
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,000
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,168
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	187
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	581
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,000
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,168
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	3.85%
Since Inception	rr_AverageAnnualReturnSinceInception	7.22%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	86
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	270
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	470
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,048
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.68%
Since Inception	rr_AverageAnnualReturnSinceInception	8.29%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	187
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	581
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,000
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,168
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	4.74%
Since Inception	rr_AverageAnnualReturnSinceInception	7.22%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.35%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.34%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	136
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	427
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	738
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,623
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.16%
Since Inception	rr_AverageAnnualReturnSinceInception	7.73%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.09%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	111
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	349
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	605
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,339
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.42%
Since Inception	rr_AverageAnnualReturnSinceInception	7.98%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	86
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	270
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	470
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,048
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.79%
Since Inception	rr_AverageAnnualReturnSinceInception	8.30%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R5
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.85%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	86
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	270
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	470
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,048
Label	rr_AverageAnnualReturnLabel	R5 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.68%
Since Inception	rr_AverageAnnualReturnSinceInception	8.29%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 02, 2010

[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 1.10% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 1.85% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.85% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.35% of the fund's average daily net assets annually for Class R2 shares, and 0.84% 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 September 30, 2013.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Summary of Key Information
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the fund is to seek a high level of total return consistent with an aggressive level of risk relative to the other MFS Asset Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth Allocation Fund, and MFS Aggressive Growth Allocation Fund.)
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 9 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 of the fund's statement of additional information Part I.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in "Annual Fund Operating Expenses" or in the "Example," affect the fund's performance.  During the most recent fiscal year, the fund's portfolio turnover rate was 11% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	11.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is designed to provide diversification among different asset classes by investing its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's investment adviser), referred to as underlying funds. The underlying funds are selected following a two stage asset allocation process. The first stage is a strategic asset allocation to determine the percentage of the fund's assets to be invested in the general asset classes of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an allocation to underlying funds that have less traditional investment strategies that MFS believes provide diversification benefits when added to a portfolio consisting of stock and bond funds (referred to as Specialty Funds). The second stage involves the actual selection of underlying funds to represent the asset classes based on underlying fund classifications, historical risk, performance, and other factors. Within the stock fund allocations, MFS seeks to diversify globally (by including domestic and international underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds), and by style (by including both growth and value underlying funds). As of September 28, 2012, the fund's target allocation among asset classes and the underlying funds was: Bond Funds:                              0% Specialty Funds:                        10% MFS Commodity Strategy Fund              5% MFS Global Real Estate Fund              5% International Stock Funds:              30% MFS Emerging Markets Equity Fund         2% MFS International Growth Fund            8% MFS International New Discovery Fund     4% MFS International Value Fund             8% MFS Research International Fund          8% U.S. Stock Funds:                       60% MFS Growth Fund                         13% MFS Mid Cap Growth Fund                 10% MFS Mid Cap Value Fund                  10% MFS New Discovery Fund                 2.5% MFS New Discovery Value Fund           2.5% MFS Research Fund                        9% MFS Value Fund                          13%
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 and underlying funds 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. 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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.    Commodity Risk:  The value of commodities may be more volatile than the value of equity securities or debt instruments and their value may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The price of a commodity may be affected by demand/supply imbalances in the market for the commodity. 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; property tax rates, 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 six-month period ended June 30, 2012 was 7.42%. During the period(s) shown in the bar chart, the highest quarterly return was 19.81% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (24.63)% (for the calendar quarter ended December 31, 2008).
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, 2011)
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | Standard & Poor's 500 Stock Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
1 Year	rr_AverageAnnualReturnYear01	2.11%
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.59%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | MFS Aggressive Growth Allocation Fund Blended Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Aggressive Growth Allocation Fund Blended Index	[1]
1 Year	rr_AverageAnnualReturnYear01	(3.32%)
5 Years	rr_AverageAnnualReturnYear05	(1.25%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.76%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[2]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.26%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.24%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	694
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	950
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,225
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,008
Annual Return 2003	rr_AnnualReturn2003	31.88%
Annual Return 2004	rr_AnnualReturn2004	15.21%
Annual Return 2005	rr_AnnualReturn2005	7.32%
Annual Return 2006	rr_AnnualReturn2006	13.06%
Annual Return 2007	rr_AnnualReturn2007	9.23%
Annual Return 2008	rr_AnnualReturn2008	(40.48%)
Annual Return 2009	rr_AnnualReturn2009	35.87%
Annual Return 2010	rr_AnnualReturn2010	18.45%
Annual Return 2011	rr_AnnualReturn2011	(4.98%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	7.42%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	19.81%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	the lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(24.63%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.44%)
5 Years	rr_AverageAnnualReturnYear05	(1.29%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.67%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(10.68%)
5 Years	rr_AverageAnnualReturnYear05	(1.79%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.27%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(6.56%)
5 Years	rr_AverageAnnualReturnYear05	(1.18%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.99%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.99%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	602
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	929
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,281
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,143
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	202
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	629
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,081
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,143
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.53%)
5 Years	rr_AverageAnnualReturnYear05	(1.18%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.77%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.99%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	302
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	629
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,081
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,336
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	202
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	629
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,081
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,336
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(6.61%)
5 Years	rr_AverageAnnualReturnYear05	(0.82%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.63%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.99%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	101
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	320
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	556
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,234
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.82%)
5 Years	rr_AverageAnnualReturnYear05	0.17%
Since Inception	rr_AverageAnnualReturnSinceInception	5.68%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529A
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.36%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.07%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.29%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	699
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	974
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,271
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,110
Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.61%)
5 Years	rr_AverageAnnualReturnYear05	(1.43%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.50%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.11%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.07%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.04%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	607
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	954
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,328
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,245
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	207
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	654
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,128
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,245
Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.59%)
5 Years	rr_AverageAnnualReturnYear05	(1.32%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.52%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.11%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.07%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.04%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	307
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	654
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,128
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,436
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	207
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	654
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,128
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,436
Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(6.71%)
5 Years	rr_AverageAnnualReturnYear05	(0.96%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.43%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.99%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	202
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	629
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,081
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,336
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.70%)
5 Years	rr_AverageAnnualReturnYear05	(0.85%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.53%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.51%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.49%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	152
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	475
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	822
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,800
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.27%)
5 Years	rr_AverageAnnualReturnYear05	(0.37%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.26%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.24%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	126
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	398
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	690
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,521
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.00%)
5 Years	rr_AverageAnnualReturnYear05	(0.11%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.32%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.86%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.01%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.02%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.99%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	101
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	320
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	556
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,234
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.80%)
5 Years	rr_AverageAnnualReturnYear05	0.15%
Since Inception	rr_AverageAnnualReturnSinceInception	5.61%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002

[1] The MFS Aggressive Growth Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (60%) Standard & Poor's 500 Stock Index; (30%) MSCI EAFE (Europe, Australasia, Far East) Index; (5%) The Dow Jones-UBS Commodity Index; and (5%) FTSE EPRA/NAREIT Developed Real Estate Index.

[2] 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.

[3] Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding program management fees, management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, such that "Other Expenses" do not exceed 0.13% of the fund's average daily net asset annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013. In addition, MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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):
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in "Annual Fund Operating Expenses" or in the "Example," affect the fund's performance.   During the most recent fiscal year, the fund's portfolio turnover rate was 15% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	15.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund's assets primarily in foreign equity securities, including emerging market equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, and depositary receipts for those securities. 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 focuses on investing the fund's assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).    MFS may invest the fund's assets in companies of any size.    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.    Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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, or 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.    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 six-month period ended June 30, 2012 was 6.11%. During the period(s) shown in the bar chart, the highest quarterly return was 22.56% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (16.30)% (for the calendar quarter ended September 30, 2008).
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, 2011)
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | MSCI EAFE (Europe, Australasia, Far East) Value Index (gross div)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI EAFE (Europe, Australasia, Far East) Value Index (gross div)
1 Year	rr_AverageAnnualReturnYear01	(11.65%)
5 Years	rr_AverageAnnualReturnYear05	(5.77%)
10 Years	rr_AverageAnnualReturnYear10	5.53%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | MSCI EAFE (Europe, Australasia, Far East) Index (gross div)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI EAFE (Europe, Australasia, Far East) Index (gross div)
1 Year	rr_AverageAnnualReturnYear01	(11.73%)
5 Years	rr_AverageAnnualReturnYear05	(4.26%)
10 Years	rr_AverageAnnualReturnYear10	5.12%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.21%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	691
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	937
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,202
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,957
Annual Return 2002	rr_AnnualReturn2002	(6.95%)
Annual Return 2003	rr_AnnualReturn2003	32.03%
Annual Return 2004	rr_AnnualReturn2004	26.77%
Annual Return 2005	rr_AnnualReturn2005	14.25%
Annual Return 2006	rr_AnnualReturn2006	28.08%
Annual Return 2007	rr_AnnualReturn2007	7.15%
Annual Return 2008	rr_AnnualReturn2008	(31.91%)
Annual Return 2009	rr_AnnualReturn2009	24.64%
Annual Return 2010	rr_AnnualReturn2010	9.13%
Annual Return 2011	rr_AnnualReturn2011	(1.96%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	6.11%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.56%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(16.30%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(7.60%)
5 Years	rr_AverageAnnualReturnYear05	(1.72%)
10 Years	rr_AverageAnnualReturnYear10	7.65%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(7.68%)
5 Years	rr_AverageAnnualReturnYear05	(2.31%)
10 Years	rr_AverageAnnualReturnYear10	6.91%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(4.55%)
5 Years	rr_AverageAnnualReturnYear05	(1.47%)
10 Years	rr_AverageAnnualReturnYear10	6.62%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.96%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	599
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	915
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,257
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,091
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	199
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	615
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,057
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,091
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(6.54%)
5 Years	rr_AverageAnnualReturnYear05	(1.58%)
10 Years	rr_AverageAnnualReturnYear10	7.75%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.96%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	299
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	615
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,057
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,285
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	199
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	615
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,057
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,285
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(3.63%)
5 Years	rr_AverageAnnualReturnYear05	(1.25%)
10 Years	rr_AverageAnnualReturnYear10	7.60%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.96%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	98
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	306
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	531
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,178
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(1.69%)
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
10 Years	rr_AverageAnnualReturnYear10	8.69%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.96%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	199
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	615
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,057
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,285
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.70%)
5 Years	rr_AverageAnnualReturnYear05	(1.25%)
10 Years	rr_AverageAnnualReturnYear10	7.60%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.46%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	149
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	462
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	797
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,746
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.18%)
5 Years	rr_AverageAnnualReturnYear05	(0.76%)
10 Years	rr_AverageAnnualReturnYear10	8.14%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.21%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	123
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	384
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	665
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,466
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(1.92%)
5 Years	rr_AverageAnnualReturnYear05	(0.50%)
10 Years	rr_AverageAnnualReturnYear10	8.41%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.96%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	98
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	306
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	531
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,178
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(1.72%)
5 Years	rr_AverageAnnualReturnYear05	(0.27%)
10 Years	rr_AverageAnnualReturnYear10	8.68%
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R5
Management Fee	rr_ManagementFeesOverAssets	0.78%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.86%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	88
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	274
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	477
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,061
Label	rr_AverageAnnualReturnLabel	R5 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(1.81%)
5 Years	rr_AverageAnnualReturnYear05	(0.34%)
10 Years	rr_AverageAnnualReturnYear10	8.58%

[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 [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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-16 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 39% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	39.00%
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 foreign equity securities, including emerging market equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, and depositary receipts for those securities. 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 focuses on investing the fund's assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies).    MFS may invest the fund's assets in companies of any size.    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.    Foreign and Emerging Markets Risk: Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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, or 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.    Growth Company Risk: The stocks of growth companies can be more sensitive to the company's earnings and more volatile than the market in general.    Investment Selection Risk: MFS' investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.    Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty's or third party's ability to perform in accordance with the terms of the transaction.    Liquidity Risk: It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.    The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-225-2606
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	mfs.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Class A Bar Chart.
Bar Chart Narrative [Text Block]	rr_BarChartNarrativeTextBlock	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total return for the six-month period ended June 30, 2012 was 6.25%. During the period(s) shown in the bar chart, the highest quarterly return was 23.27% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (19.64)% (for the calendar quarter ended September 30, 2011).
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, 2011)
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | MSCI All Country World (ex-US) Growth Index (gross div)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI All Country World (ex-US) Growth Index (gross div)
1 Year	rr_AverageAnnualReturnYear01	(13.93%)
5 Years	rr_AverageAnnualReturnYear05	(1.84%)
10 Years	rr_AverageAnnualReturnYear10	5.94%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.37%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	706
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	984
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,282
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,127
Annual Return 2002	rr_AnnualReturn2002	(12.13%)
Annual Return 2003	rr_AnnualReturn2003	36.03%
Annual Return 2004	rr_AnnualReturn2004	17.54%
Annual Return 2005	rr_AnnualReturn2005	13.95%
Annual Return 2006	rr_AnnualReturn2006	25.72%
Annual Return 2007	rr_AnnualReturn2007	15.90%
Annual Return 2008	rr_AnnualReturn2008	(40.10%)
Annual Return 2009	rr_AnnualReturn2009	37.65%
Annual Return 2010	rr_AnnualReturn2010	14.99%
Annual Return 2011	rr_AnnualReturn2011	(10.85%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	6.25%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	23.27%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(19.64%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(15.97%)
5 Years	rr_AverageAnnualReturnYear05	(1.58%)
10 Years	rr_AverageAnnualReturnYear10	6.39%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(15.96%)
5 Years	rr_AverageAnnualReturnYear05	(2.00%)
10 Years	rr_AverageAnnualReturnYear10	5.94%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(10.11%)
5 Years	rr_AverageAnnualReturnYear05	(1.31%)
10 Years	rr_AverageAnnualReturnYear10	5.57%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.12%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	615
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	964
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,339
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,261
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	215
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	664
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,139
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,261
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(15.03%)
5 Years	rr_AverageAnnualReturnYear05	(1.47%)
10 Years	rr_AverageAnnualReturnYear10	6.49%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.12%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	315
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	664
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,139
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,452
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	215
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	664
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,139
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,452
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(12.42%)
5 Years	rr_AverageAnnualReturnYear05	(1.12%)
10 Years	rr_AverageAnnualReturnYear10	6.33%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.12%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	114
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	356
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	617
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,363
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.62%)
5 Years	rr_AverageAnnualReturnYear05	(0.12%)
10 Years	rr_AverageAnnualReturnYear10	7.63%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.12%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	215
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	664
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,139
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,452
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(11.52%)
5 Years	rr_AverageAnnualReturnYear05	(1.12%)
10 Years	rr_AverageAnnualReturnYear10	6.33%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.62%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	165
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	511
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	881
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,922
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(11.06%)
5 Years	rr_AverageAnnualReturnYear05	(0.62%)
10 Years	rr_AverageAnnualReturnYear10	6.87%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.37%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	139
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	434
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	750
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,646
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.80%)
5 Years	rr_AverageAnnualReturnYear05	(0.37%)
10 Years	rr_AverageAnnualReturnYear10	7.14%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.27%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.12%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	114
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	356
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	617
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,363
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.63%)
5 Years	rr_AverageAnnualReturnYear05	(0.13%)
10 Years	rr_AverageAnnualReturnYear10	7.40%
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R5
Management Fee	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.17%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.02%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	104
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	325
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	563
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,248
Label	rr_AverageAnnualReturnLabel	R5 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.70%)
5 Years	rr_AverageAnnualReturnYear05	(0.22%)
10 Years	rr_AverageAnnualReturnYear10	7.29%

[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 [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Summary of Key Information
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the fund is to seek a high level of total return consistent with a greater than moderate level of risk relative to the other MFS Asset Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth Allocation Fund, and MFS Aggressive Growth Allocation Fund.)
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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 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 7% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	7.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is designed to provide diversification among different asset classes by investing its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's investment adviser), referred to as underlying funds. The underlying funds are selected following a two stage asset allocation process. The first stage is a strategic asset allocation to determine the percentage of the fund's assets to be invested in the general asset classes of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an allocation to underlying funds that have less traditional investment strategies that MFS believes provide diversification benefits when added to a portfolio consisting of stock and bond funds (referred to as Specialty Funds). The second stage involves the actual selection of underlying funds to represent the asset classes based on underlying fund classifications, historical risk, performance, and other factors. Within the stock fund allocations, MFS seeks to diversify globally (by including domestic and international underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds), and by style (by including both growth and value underlying funds). Within the bond fund allocation, MFS includes underlying funds with varying degrees of interest rate and credit exposure. As of September 28, 2012, the fund's target allocation among asset classes and the underlying funds was: Bond Funds:                            20% MFS Emerging Markets Debt Fund          3% MFS Global Bond Fund                    4% MFS High Income Fund                    5% MFS Inflation-Adjusted Bond Fund        5% MFS Research Bond Fund                  3% Specialty Funds:                        8% MFS Absolute Return Fund                1% MFS Commodity Strategy Fund             4% MFS Global Real Estate Fund             3% International Stock Funds:             20% MFS Emerging Markets Equity Fund        1% MFS International Growth Fund           5% MFS International New Discovery Fund    2% MFS International Value Fund            5% MFS Research International Fund         7% U.S. Stock Funds:                      52% MFS Growth Fund                        11% MFS Mid Cap Growth Fund                 9% MFS Mid Cap Value Fund                  9% MFS New Discovery Fund                  2% MFS New Discovery Value Fund            2% MFS Research Fund                       8% MFS Value Fund                         11%
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 and underlying funds 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. 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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. 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, or 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. 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. Commodity Risk:  The value of commodities may be more volatile than the value of equity securities or debt instruments and their value may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The price of a commodity may be affected by demand/supply imbalances in the market for the commodity. 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; property tax rates, 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 six-month period ended June 30, 2012 was 6.92%. During the period(s) shown in the bar chart, the highest quarterly return was 17.14% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (20.20)% (for the calendar quarter ended December 31, 2008).
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, 2011)
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | Standard & Poor's 500 Stock Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
1 Year	rr_AverageAnnualReturnYear01	2.11%
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.59%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | MFS Growth Allocation Fund Blended Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Growth Allocation Fund Blended Index	[1]
1 Year	rr_AverageAnnualReturnYear01	(0.24%)
5 Years	rr_AverageAnnualReturnYear05	0.58%
Since Inception	rr_AverageAnnualReturnSinceInception	5.33%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[2]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.17%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.17%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	687
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	925
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,182
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,914
Annual Return 2003	rr_AnnualReturn2003	26.16%
Annual Return 2004	rr_AnnualReturn2004	13.75%
Annual Return 2005	rr_AnnualReturn2005	6.66%
Annual Return 2006	rr_AnnualReturn2006	12.61%
Annual Return 2007	rr_AnnualReturn2007	8.85%
Annual Return 2008	rr_AnnualReturn2008	(34.42%)
Annual Return 2009	rr_AnnualReturn2009	32.33%
Annual Return 2010	rr_AnnualReturn2010	16.71%
Annual Return 2011	rr_AnnualReturn2011	(2.33%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	6.92%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	17.14%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(20.20%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(7.94%)
5 Years	rr_AverageAnnualReturnYear05	0.30%
Since Inception	rr_AverageAnnualReturnSinceInception	5.28%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(8.46%)
5 Years	rr_AverageAnnualReturnYear05	(0.49%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.61%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(4.96%)
5 Years	rr_AverageAnnualReturnYear05	(0.05%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.33%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.92%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.92%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	595
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	903
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,237
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,048
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	195
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	603
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,037
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,048
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(6.90%)
5 Years	rr_AverageAnnualReturnYear05	0.44%
Since Inception	rr_AverageAnnualReturnSinceInception	5.34%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.92%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.92%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	295
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	603
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,037
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,243
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	195
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	603
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,037
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,243
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.06%)
5 Years	rr_AverageAnnualReturnYear05	0.78%
Since Inception	rr_AverageAnnualReturnSinceInception	5.22%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.92%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	0.92%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	94
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	293
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	509
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,131
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.01%)
5 Years	rr_AverageAnnualReturnYear05	1.80%
Since Inception	rr_AverageAnnualReturnSinceInception	6.28%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529A
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.27%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.22%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	692
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	950
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,227
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,017
Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(7.96%)
5 Years	rr_AverageAnnualReturnYear05	0.18%
Since Inception	rr_AverageAnnualReturnSinceInception	5.08%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.02%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.97%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	600
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	929
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,283
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,151
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	200
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	629
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,083
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,151
Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(6.88%)
5 Years	rr_AverageAnnualReturnYear05	0.31%
Since Inception	rr_AverageAnnualReturnSinceInception	5.13%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.02%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.97%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	300
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	629
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,083
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,344
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	200
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	629
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,083
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,344
Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.10%)
5 Years	rr_AverageAnnualReturnYear05	0.65%
Since Inception	rr_AverageAnnualReturnSinceInception	5.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.92%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.92%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	195
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	603
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,037
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,243
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(3.00%)
5 Years	rr_AverageAnnualReturnYear05	0.77%
Since Inception	rr_AverageAnnualReturnSinceInception	5.13%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.42%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.42%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	145
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	449
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	776
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,702
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.58%)
5 Years	rr_AverageAnnualReturnYear05	1.25%
Since Inception	rr_AverageAnnualReturnSinceInception	5.61%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.17%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	1.17%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	119
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	372
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	644
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,420
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.33%)
5 Years	rr_AverageAnnualReturnYear05	1.51%
Since Inception	rr_AverageAnnualReturnSinceInception	5.91%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.11%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.81%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.92%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements	rr_NetExpensesOverAssets	0.92%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	94
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	293
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	509
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,131
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.09%)
5 Years	rr_AverageAnnualReturnYear05	1.79%
Since Inception	rr_AverageAnnualReturnSinceInception	6.22%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002

[1] The MFS Growth Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (52%) Standard & Poor's 500 Stock Index; (20%) MSCI EAFE (Europe, Australasia, Far East) Index; (4%) The Dow Jones-UBS Commodity Index; (3%) FTSE EPRA/NAREIT Developed Real Estate Index; and (21%) Barclays U.S. Aggregate Bond Index.

[2] 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.

[3] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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 for Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect current fee arrangements. The annual fund operating expenses for Class R5 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 7 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 28% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	28.00%
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
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The annual fund operating expenses for Class R5 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.
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 equity securities of issuers that are tied economically to emerging market countries. Emerging market countries include countries located in Latin America, Asia, Africa, the Middle East, and developing countries of Europe, primarily Eastern Europe. MFS may also invest in equity securities of issuers that are not tied economically to emerging market countries. Equity securities include common stocks, preferred stocks, securities convertible into stocks, and depositary receipts for those securities. MFS may invest the fund's assets in companies of any size. 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 may invest a relatively large percentage of the fund's assets in a single issuer or a small number of issuers. 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. Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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, or 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. Issuer Focus Risk:  The fund's performance could be more volatile than the performance of more 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. Counterparty and Third Party Risk:  Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty's or third party's ability to perform in accordance with the terms of the transaction. Liquidity Risk:  It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance. The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-225-2606
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	mfs.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Class A Bar Chart.
Bar Chart Narrative [Text Block]	rr_BarChartNarrativeTextBlock	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total return for the six-month period ended June 30, 2012 was 5.55%. During the period(s) shown in the bar chart, the highest quarterly return was 30.53% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (30.59)% (for the calendar quarter ended September 30, 2008).
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, 2011)
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | MSCI Emerging Markets Index (gross div)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI Emerging Markets Index (gross div)
1 Year	rr_AverageAnnualReturnYear01	(18.17%)
5 Years	rr_AverageAnnualReturnYear05	2.70%
10 Years	rr_AverageAnnualReturnYear10	14.20%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.72%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.71%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	739
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	1,085
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,454
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,488
Annual Return 2002	rr_AnnualReturn2002	(2.84%)
Annual Return 2003	rr_AnnualReturn2003	52.02%
Annual Return 2004	rr_AnnualReturn2004	26.71%
Annual Return 2005	rr_AnnualReturn2005	35.48%
Annual Return 2006	rr_AnnualReturn2006	29.75%
Annual Return 2007	rr_AnnualReturn2007	35.46%
Annual Return 2008	rr_AnnualReturn2008	(55.55%)
Annual Return 2009	rr_AnnualReturn2009	68.10%
Annual Return 2010	rr_AnnualReturn2010	23.07%
Annual Return 2011	rr_AnnualReturn2011	(18.81%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	5.55%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	30.53%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(30.59%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(23.48%)
5 Years	rr_AverageAnnualReturnYear05	(0.95%)
10 Years	rr_AverageAnnualReturnYear10	12.11%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(23.37%)
5 Years	rr_AverageAnnualReturnYear05	(1.70%)
10 Years	rr_AverageAnnualReturnYear10	11.36%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(15.01%)
5 Years	rr_AverageAnnualReturnYear05	(0.76%)
10 Years	rr_AverageAnnualReturnYear10	10.83%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.47%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.46%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	649
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	1,069
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,515
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,621
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	249
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	769
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,315
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,621
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(22.65%)
5 Years	rr_AverageAnnualReturnYear05	(0.78%)
10 Years	rr_AverageAnnualReturnYear10	12.22%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.47%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.46%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	349
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	769
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,315
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,805
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	249
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	769
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,315
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,805
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(20.20%)
5 Years	rr_AverageAnnualReturnYear05	(0.48%)
10 Years	rr_AverageAnnualReturnYear10	12.05%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.47%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.46%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	149
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	464
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	802
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,757
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(18.61%)
5 Years	rr_AverageAnnualReturnYear05	0.51%
10 Years	rr_AverageAnnualReturnYear10	13.17%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.47%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.46%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	249
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	769
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,315
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,805
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(19.40%)
5 Years	rr_AverageAnnualReturnYear05	(0.48%)
10 Years	rr_AverageAnnualReturnYear10	12.05%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.97%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.96%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	199
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	617
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,061
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,295
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(19.02%)
5 Years	rr_AverageAnnualReturnYear05	0.02%
10 Years	rr_AverageAnnualReturnYear10	12.61%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.72%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.71%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	174
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	541
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	932
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,029
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(18.82%)
5 Years	rr_AverageAnnualReturnYear05	0.26%
10 Years	rr_AverageAnnualReturnYear10	12.89%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.43%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.47%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.46%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	149
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	464
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	802
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,757
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(18.61%)
5 Years	rr_AverageAnnualReturnYear05	0.52%
10 Years	rr_AverageAnnualReturnYear10	13.18%
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R5
Management Fee	rr_ManagementFeesOverAssets	1.04%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.37%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.36%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	138
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	433
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	749
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,645
Label	rr_AverageAnnualReturnLabel	R5 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(18.61%)
5 Years	rr_AverageAnnualReturnYear05	0.51%
10 Years	rr_AverageAnnualReturnYear10	13.17%

[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] Effective October 1, 2012, MFS has agreed in writing to reduce the management fee to 0.95% of the fund's average daily net assets annually in excess of $500 million up to $2.5 billion, and 0.90% of the fund's average daily net assets annually in excess of $2.5 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Summary of Key Information
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the fund is to seek a high level of total return consistent with a conservative level of risk relative to the other MFS Asset Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth Allocation Fund, and MFS Aggressive Growth Allocation Fund.)
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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 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 4% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	4.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is designed to provide diversification among different asset classes by investing its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's investment adviser), referred to as underlying funds. The underlying funds are selected following a two stage asset allocation process. The first stage is a strategic asset allocation to determine the percentage of the fund's assets to be invested in the general asset classes of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an allocation to underlying funds that have less traditional investment strategies that MFS believes provide diversification benefits when added to a portfolio consisting of stock and bond funds (referred to as Specialty Funds). The second stage involves the actual selection of underlying funds to represent the asset classes based on underlying fund classifications, historical risk, performance, and other factors. Within the stock fund allocations, MFS seeks to diversify globally (by including domestic and international underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds), and by style (by including both growth and value underlying funds). Within the bond fund allocation, MFS includes underlying funds with varying degrees of interest rate and credit exposure. As of September 28, 2012, the fund's target allocation among asset classes and the underlying funds was: Bond Funds:                        60% MFS Emerging Markets Debt Fund      3% MFS Global Bond Fund                5% MFS Government Securities Fund     10% MFS High Income Fund                5% MFS Inflation-Adjusted Bond Fund   10% MFS Limited Maturity Fund          10% MFS Research Bond Fund             17% Specialty Funds:                    4% MFS Absolute Return Fund            2% MFS Commodity Strategy Fund         1% MFS Global Real Estate Fund         1% International Stock Funds:          8% MFS International Growth Fund       2% MFS International Value Fund        2% MFS Research International Fund     4% U.S. Stock Funds:                  28% MFS Growth Fund                     6% MFS Mid Cap Growth Fund             4% MFS Mid Cap Value Fund              4% MFS New Discovery Fund              1% MFS New Discovery Value Fund        1% MFS Research Fund                   6% MFS Value Fund                      6%
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 and underlying funds 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, or 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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. Commodity Risk:  The value of commodities may be more volatile than the value of equity securities or debt instruments and their value may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The price of a commodity may be affected by demand/supply imbalances in the market for the commodity. 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; property tax rates, 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. 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. 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 six-month period ended June 30, 2012 was 4.93%. During the period(s) shown in the bar chart, the highest quarterly return was 10.76% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (9.28)% (for the calendar quarter ended December 31, 2008).
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, 2011)
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | Barclays U.S. Aggregate Bond Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Aggregate Bond Index
1 Year	rr_AverageAnnualReturnYear01	7.84%
5 Years	rr_AverageAnnualReturnYear05	6.50%
Since Inception	rr_AverageAnnualReturnSinceInception	5.64%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | MFS Conservative Allocation Fund Blended Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Conservative Allocation Fund Blended Index	[1]
1 Year	rr_AverageAnnualReturnYear01	4.58%
5 Years	rr_AverageAnnualReturnYear05	3.81%
Since Inception	rr_AverageAnnualReturnSinceInception	5.43%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[2]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.03%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.03%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	674
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	884
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,111
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,762
Annual Return 2003	rr_AnnualReturn2003	11.65%
Annual Return 2004	rr_AnnualReturn2004	7.23%
Annual Return 2005	rr_AnnualReturn2005	3.94%
Annual Return 2006	rr_AnnualReturn2006	8.65%
Annual Return 2007	rr_AnnualReturn2007	7.33%
Annual Return 2008	rr_AnnualReturn2008	(16.60%)
Annual Return 2009	rr_AnnualReturn2009	22.15%
Annual Return 2010	rr_AnnualReturn2010	11.29%
Annual Return 2011	rr_AnnualReturn2011	2.43%
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	4.93%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	10.76%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	the lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(9.28%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(3.46%)
5 Years	rr_AverageAnnualReturnYear05	3.27%
Since Inception	rr_AverageAnnualReturnSinceInception	4.82%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(4.33%)
5 Years	rr_AverageAnnualReturnYear05	2.23%
Since Inception	rr_AverageAnnualReturnSinceInception	3.93%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(2.16%)
5 Years	rr_AverageAnnualReturnYear05	2.25%
Since Inception	rr_AverageAnnualReturnSinceInception	3.70%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.78%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	581
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	860
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,164
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,897
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	181
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	560
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	964
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,897
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.33%)
5 Years	rr_AverageAnnualReturnYear05	3.43%
Since Inception	rr_AverageAnnualReturnSinceInception	4.89%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.78%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	281
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	560
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	964
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,095
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	181
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	560
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	964
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,095
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	0.64%
5 Years	rr_AverageAnnualReturnYear05	3.78%
Since Inception	rr_AverageAnnualReturnSinceInception	4.77%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.78%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	80
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	249
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	433
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	966
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.65%
5 Years	rr_AverageAnnualReturnYear05	4.81%
Since Inception	rr_AverageAnnualReturnSinceInception	5.82%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529A
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.13%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.08%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	679
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	909
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,157
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,866
Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(3.53%)
5 Years	rr_AverageAnnualReturnYear05	3.14%
Since Inception	rr_AverageAnnualReturnSinceInception	4.63%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.88%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.83%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	586
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	886
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,211
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,001
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	186
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	586
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,011
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,001
Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(2.34%)
5 Years	rr_AverageAnnualReturnYear05	3.30%
Since Inception	rr_AverageAnnualReturnSinceInception	4.69%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.88%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.83%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	286
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	586
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,011
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,197
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	186
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	586
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,011
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,197
Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	0.64%
5 Years	rr_AverageAnnualReturnYear05	3.64%
Since Inception	rr_AverageAnnualReturnSinceInception	4.58%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.78%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	181
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	560
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	964
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,095
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	1.66%
5 Years	rr_AverageAnnualReturnYear05	3.74%
Since Inception	rr_AverageAnnualReturnSinceInception	4.68%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.28%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.28%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	130
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	406
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	702
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,545
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.22%
5 Years	rr_AverageAnnualReturnYear05	4.27%
Since Inception	rr_AverageAnnualReturnSinceInception	5.16%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.03%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.03%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	105
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	328
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	569
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,259
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.36%
5 Years	rr_AverageAnnualReturnYear05	4.51%
Since Inception	rr_AverageAnnualReturnSinceInception	5.47%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.69%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.78%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	80
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	249
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	433
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	966
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.75%
5 Years	rr_AverageAnnualReturnYear05	4.80%
Since Inception	rr_AverageAnnualReturnSinceInception	5.77%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002

[1] The MFS Conservative Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (28%) Standard & Poor's 500 Stock Index; (8%) MSCI EAFE (Europe, Australasia, Far East) Index; (1%) The Dow Jones-UBS Commodity Index; (1%) FTSE EPRA/NAREIT Developed Real Estate Index; and (62%) Barclays U.S. Aggregate Bond Index.

[2] 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.

[3] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

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MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification 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 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 International Diversification Fund	A		B	C	I	529A	529B	529C	R1	R2	R3	R4
Shareholder Fees Column [Text]	A		B	C	I	529A	529B	529C	ALL R	ALL R	ALL R	ALL R
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	5.75%	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	4.00%	1.00%	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 International Diversification Fund		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Operating Expenses Column [Text]		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Management Fee		none	none	none	none	none	none	none	none	none	none	none
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	0.25%	1.00%	1.00%	1.00%	0.50%	0.25%	none
Other Expenses		0.13%	0.13%	0.13%	0.13%	0.23%	0.23%	0.23%	0.13%	0.13%	0.13%	0.13%
Acquired (Underlying) Fund		0.97%	0.97%	0.97%	0.97%	0.97%	0.97%	0.97%	0.97%	0.97%	0.97%	0.97%
Total Annual Fund Operating Expenses		1.35%	2.10%	2.10%	1.10%	1.45%	2.20%	2.20%	2.10%	1.60%	1.35%	1.10%
Fee Reductions and/or Expense Reimbursements	[1]	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.08%)	(0.08%)	(0.08%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.32%	2.07%	2.07%	1.07%	1.37%	2.12%	2.12%	2.07%	1.57%	1.32%	1.07%

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 International Diversification Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	702	975	1,269	2,103
B	Class B Shares assuming redemption at end of period	610	955	1,326	2,237
C	Class C Shares assuming redemption at end of period	310	655	1,126	2,429
I	Class I Shares	109	347	603	1,338
529A	Class 529A Shares	706	992	1,307	2,197
529B	Class 529B Shares assuming redemption at end of period	615	972	1,365	2,331
529C	Class 529C Shares Assuming redemption at end of period	315	672	1,165	2,521
R1	Class R1 Shares	210	655	1,126	2,429
R2	Class R2 Shares	160	502	868	1,898
R3	Class R3 Shares	134	425	737	1,621
R4	Class R4 Shares	109	347	603	1,338

Expense Example, No Redemption MFS International Diversification Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	210	655	1,126	2,237
C	Class C Shares assuming no redemption at end of period	210	655	1,126	2,429
529B	Class 529B Shares assuming no redemption at end of period	215	672	1,165	2,331
529C	Class 529C Shares Assuming no redemption at end of period	215	672	1,165	2,521

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 8% of
the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification within the international asset
class by investing the majority of its assets in other mutual funds advised by
MFS (Massachusetts Financial Services Company, the fund's Investment adviser),
referred to as underlying funds. The underlying funds are selected based on
underlying fund classifications, historical risk, performance, and other
factors. MFS seeks to diversify the fund's investments in terms of market
capitalization (by including large, mid, and/or small cap underlying funds), by
style (by including both growth and value underlying funds), and by geographic
region (by including developed and emerging market underlying funds). However,
MFS may invest a relatively large percentage of the underlying funds' assets in
a single country, a small number of countries, or a particular geographic region.
As of September 28, 2012, the fund's target allocation among underlying funds was:
  
MFS Emerging Markets Equity Fund       10%
MFS International Growth Fund          25%
MFS International New Discovery Fund   10%
MFS International Value Fund           25%
MFS Research International Fund        30%

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 and underlying funds 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.
  
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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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, or 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.
  
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.

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

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

Class A Bar Chart.

The total return for the six-month period ended June 30, 2012 was 5.68%.  During
the period(s) shown in the bar chart, the highest quarterly return was 23.90%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (19.72)% (for the calendar quarter ended September 30, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS International Diversification Fund	Label	1 Year	5 Years	Since Inception	Inception Date
A	A Shares Returns Before Taxes	(14.61%)	(2.65%)	5.65%	Sep. 30, 2004
B	B Shares Returns Before Taxes	(13.71%)	(2.52%)	5.79%	Sep. 30, 2004
C	C Shares Returns Before Taxes	(10.97%)	(2.18%)	5.78%	Sep. 30, 2004
I	I Shares Returns Before Taxes	(9.17%)	(1.18%)	6.85%	Sep. 30, 2004
529A	529A Shares Returns Before Taxes	(14.71%)	(2.79%)	5.45%	Sep. 30, 2004
529B	529B Shares Returns Before Taxes	(13.71%)	(2.66%)	5.60%	Sep. 30, 2004
529C	529C Shares Returns Before Taxes	(11.10%)	(2.30%)	5.61%	Sep. 30, 2004
R1	R1 Shares Returns Before Taxes	(10.10%)	(2.21%)	5.71%	Sep. 30, 2004
R2	R2 Shares Returns Before Taxes	(9.70%)	(1.72%)	6.22%	Sep. 30, 2004
R3	R3 Shares Returns Before Taxes	(9.43%)	(1.48%)	6.49%	Sep. 30, 2004
R4	R4 Shares Returns Before Taxes	(9.13%)	(1.24%)	6.78%	Sep. 30, 2004
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(14.72%)	(3.29%)	4.86%	Sep. 30, 2004
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	(9.34%)	(2.35%)	4.70%	Sep. 30, 2004
MSCI All Country World (ex-US) Growth Index (gross div)	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI All Country World (ex-US) Index (gross div)	(13.33%)	(2.48%)	5.98%	Sep. 30, 2004

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] Effective June 1, 2012, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding program management fees, management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013. In addition, the fund's distributor, MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2014, unless MFS Fund Distributors, Inc. elects to extend the waiver.

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MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity 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 for Class A, Class B, Class C, Class I,
Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect
current fee arrangements. The annual fund operating expenses for Class R5 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 7 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 Emerging Markets Equity Fund	A		B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Shareholder Fees Column [Text]	A		B	C	I	ALL R	ALL R	ALL R	ALL R	ALL R
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 Emerging Markets Equity Fund		A	B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Operating Expenses Column [Text]		A	B	C	I	R1	R2	R3	R4	R5
Management Fee		1.04%	1.04%	1.04%	1.04%	1.04%	1.04%	1.04%	1.04%	1.04%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses		0.43%	0.43%	0.43%	0.43%	0.43%	0.43%	0.43%	0.43%	0.33%
Total Annual Fund Operating Expenses		1.72%	2.47%	2.47%	1.47%	2.47%	1.97%	1.72%	1.47%	1.37%
Fee Reductions and/or Expense Reimbursements	[1]	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)	(0.01%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.71%	2.46%	2.46%	1.46%	2.46%	1.96%	1.71%	1.46%	1.36%

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 Emerging Markets Equity Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	739	1,085	1,454	2,488
B	Class B Shares assuming redemption at end of period	649	1,069	1,515	2,621
C	Class C Shares assuming redemption at end of period	349	769	1,315	2,805
I	Class I Shares	149	464	802	1,757
Class R1	Class R1 Shares	249	769	1,315	2,805
Class R2	Class R2 Shares	199	617	1,061	2,295
Class R3	Class R3 Shares	174	541	932	2,029
Class R4	Class R4 Shares	149	464	802	1,757
Class R5	Class R5 Shares	138	433	749	1,645

Expense Example, No Redemption MFS Emerging Markets Equity Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	249	769	1,315	2,621
C	Class C Shares assuming no redemption at end of period	249	769	1,315	2,805

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 28% 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 equity securities
of issuers that are tied economically to emerging market countries. Emerging
market countries include countries located in Latin America, Asia, Africa,
the Middle East, and developing countries of Europe, primarily Eastern Europe.
MFS may also invest in equity securities of issuers that are not tied
economically to emerging market countries.

Equity securities include common stocks, preferred stocks, securities
convertible into stocks, and depositary receipts for those securities.

MFS may invest the fund's assets in companies of any size.

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 may invest a relatively large percentage of the fund's assets in a single
issuer or a small number of issuers.

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.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially
emerging markets, through issuers or currencies can involve additional risks
relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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, or 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.

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

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

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

Performance Information

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

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

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

Class A Bar Chart.

The total return for the six-month period ended June 30, 2012 was 5.55%. During
the period(s) shown in the bar chart, the highest quarterly return was 30.53%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (30.59)% (for the calendar quarter ended September 30, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Emerging Markets Equity Fund	Label	1 Year	5 Years	10 Years
A	A Shares Returns Before Taxes	(23.48%)	(0.95%)	12.11%
B	B Shares Returns Before Taxes	(22.65%)	(0.78%)	12.22%
C	C Shares Returns Before Taxes	(20.20%)	(0.48%)	12.05%
I	I Shares Returns Before Taxes	(18.61%)	0.51%	13.17%
Class R1	R1 Shares Returns Before Taxes	(19.40%)	(0.48%)	12.05%
Class R2	R2 Shares Returns Before Taxes	(19.02%)	0.02%	12.61%
Class R3	R3 Shares Returns Before Taxes	(18.82%)	0.26%	12.89%
Class R4	R4 Shares Returns Before Taxes	(18.61%)	0.52%	13.18%
Class R5	R5 Shares Returns Before Taxes	(18.61%)	0.51%	13.17%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(23.37%)	(1.70%)	11.36%
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	(15.01%)	(0.76%)	10.83%
MSCI Emerging Markets Index (gross div)	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI Emerging Markets Index (gross div)	(18.17%)	2.70%	14.20%

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] Effective October 1, 2012, MFS has agreed in writing to reduce the management fee to 0.95% of the fund's average daily net assets annually in excess of $500 million up to $2.5 billion, and 0.90% of the fund's average daily net assets annually in excess of $2.5 billion. This written agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013.

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MFS International Value Fund (Prospectus Summary) | MFS International 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 International Value Fund	A		B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Shareholder Fees Column [Text]	A		B	C	I	ALL R	ALL R	ALL R	ALL R	ALL R
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 International Value Fund	A	B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Operating Expenses Column [Text]	A	B	C	I	R1	R2	R3	R4	R5
Management Fee	0.78%	0.78%	0.78%	0.78%	0.78%	0.78%	0.78%	0.78%	0.78%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses	0.18%	0.18%	0.18%	0.18%	0.18%	0.18%	0.18%	0.18%	0.08%
Total Annual Fund Operating Expenses	1.21%	1.96%	1.96%	0.96%	1.96%	1.46%	1.21%	0.96%	0.86%

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 International Value Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	691	937	1,202	1,957
B	Class B Shares assuming redemption at end of period	599	915	1,257	2,091
C	Class C Shares assuming redemption at end of period	299	615	1,057	2,285
I	Class I Shares	98	306	531	1,178
Class R1	Class R1 Shares	199	615	1,057	2,285
Class R2	Class R2 Shares	149	462	797	1,746
Class R3	Class R3 Shares	123	384	665	1,466
Class R4	Class R4 Shares	98	306	531	1,178
Class R5	Class R5 Shares	88	274	477	1,061

Expense Example, No Redemption MFS International Value Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	199	615	1,057	2,091
C	Class C Shares assuming no redemption at end of period	199	615	1,057	2,285

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when shares are
held in a taxable account. These transaction costs, which are not reflected in
"Annual Fund Operating Expenses" or in the "Example," affect the fund's performance.  
During the most recent fiscal year, the fund's portfolio turnover rate was 15% of
the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund's investment adviser)
normally invests the fund's assets primarily in foreign equity securities,
including emerging market equity securities. Equity securities include common
stocks, preferred stocks, securities convertible into stocks, and depositary
receipts for those securities.

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 focuses on investing the fund's assets in the stocks of companies it
believes are undervalued compared to their perceived worth (value companies).
  
MFS may invest the fund's assets in companies of any size.
  
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.
  
Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially
emerging markets, through issuers or currencies can involve additional risks
relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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, or 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.
  
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 six-month period ended June 30, 2012 was 6.11%. During
the period(s) shown in the bar chart, the highest quarterly return was 22.56%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (16.30)% (for the calendar quarter ended September 30, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS International Value Fund	Label	1 Year	5 Years	10 Years
A	A Shares Returns Before Taxes	(7.60%)	(1.72%)	7.65%
B	B Shares Returns Before Taxes	(6.54%)	(1.58%)	7.75%
C	C Shares Returns Before Taxes	(3.63%)	(1.25%)	7.60%
I	I Shares Returns Before Taxes	(1.69%)	(0.25%)	8.69%
Class R1	R1 Shares Returns Before Taxes	(2.70%)	(1.25%)	7.60%
Class R2	R2 Shares Returns Before Taxes	(2.18%)	(0.76%)	8.14%
Class R3	R3 Shares Returns Before Taxes	(1.92%)	(0.50%)	8.41%
Class R4	R4 Shares Returns Before Taxes	(1.72%)	(0.27%)	8.68%
Class R5	R5 Shares Returns Before Taxes	(1.81%)	(0.34%)	8.58%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(7.68%)	(2.31%)	6.91%
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	(4.55%)	(1.47%)	6.62%
MSCI EAFE (Europe, Australasia, Far East) Value Index (gross div)	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI EAFE (Europe, Australasia, Far East) Value Index (gross div)	(11.65%)	(5.77%)	5.53%
MSCI EAFE (Europe, Australasia, Far East) Index (gross div)	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MSCI EAFE (Europe, Australasia, Far East) Index (gross div)	(11.73%)	(4.26%)	5.12%

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

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

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MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund

Summary of Key Information

Investment Objective

The investment objective of the fund is to seek a high level of total return
consistent with a conservative level of risk relative to the other MFS Asset
Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS
Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth
Allocation Fund, and MFS Aggressive Growth Allocation Fund.)

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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 of
the fund's statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Conservative Allocation Fund	A		B	C	I	529A	529B	529C	R1	R2	R3	R4
Shareholder Fees Column [Text]	A		B	C	I	529A	529B	529C	ALL R	ALL R	ALL R	ALL R
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	5.75%	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	4.00%	1.00%	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 Conservative Allocation Fund		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Operating Expenses Column [Text]		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Management Fee		none	none	none	none	none	none	none	none	none	none	none
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	0.25%	1.00%	1.00%	1.00%	0.50%	0.25%	none
Other Expenses		0.09%	0.09%	0.09%	0.09%	0.19%	0.19%	0.19%	0.09%	0.09%	0.09%	0.09%
Acquired (Underlying) Fund Fees and Expenses		0.69%	0.69%	0.69%	0.69%	0.69%	0.69%	0.69%	0.69%	0.69%	0.69%	0.69%
Total Annual Fund Operating Expenses		1.03%	1.78%	1.78%	0.78%	1.13%	1.88%	1.88%	1.78%	1.28%	1.03%	0.78%
Fee Reductions and/or Expense Reimbursements	[1]	none	none	none	none	(0.05%)	(0.05%)	(0.05%)	none	none	none	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.03%	1.78%	1.78%	0.78%	1.08%	1.83%	1.83%	1.78%	1.28%	1.03%	0.78%

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 Conservative Allocation Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	674	884	1,111	1,762
B	Class B Shares assuming redemption at end of period	581	860	1,164	1,897
C	Class C Shares assuming redemption at end of period	281	560	964	2,095
I	Class I Shares	80	249	433	966
529A	Class 529A Shares	679	909	1,157	1,866
529B	Class 529B Shares assuming redemption at end of period	586	886	1,211	2,001
529C	Class 529C Shares assuming redemption at end of period	286	586	1,011	2,197
R1	Class R1 Shares	181	560	964	2,095
R2	Class R2 Shares	130	406	702	1,545
R3	Class R3 Shares	105	328	569	1,259
R4	Class R4 Shares	80	249	433	966

Expense Example, No Redemption MFS Conservative Allocation Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	181	560	964	1,897
C	Class C Shares assuming no redemption at end of period	181	560	964	2,095
529B	Class 529B Shares assuming no redemption at end of period	186	586	1,011	2,001
529C	Class 529C Shares assuming no redemption at end of period	186	586	1,011	2,197

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 4% of the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification among different asset classes by
investing its assets in other mutual funds advised by MFS (Massachusetts
Financial Services Company, the fund's investment adviser), referred to as
underlying funds. The underlying funds are selected following a two stage asset
allocation process. The first stage is a strategic asset allocation to determine
the percentage of the fund's assets to be invested in the general asset classes
of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an
allocation to underlying funds that have less traditional investment strategies
that MFS believes provide diversification benefits when added to a portfolio
consisting of stock and bond funds (referred to as Specialty Funds). The second
stage involves the actual selection of underlying funds to represent the asset
classes based on underlying fund classifications, historical risk, performance,
and other factors. Within the stock fund allocations, MFS seeks to diversify
globally (by including domestic and international underlying funds), in terms of
market capitalization (by including large, mid, and small capitalization
underlying funds), and by style (by including both growth and value underlying
funds). Within the bond fund allocation, MFS includes underlying funds with
varying degrees of interest rate and credit exposure.

As of September 28, 2012, the fund's target allocation among asset classes and
the underlying funds was:

Bond Funds:                        60%
MFS Emerging Markets Debt Fund      3%
MFS Global Bond Fund                5%
MFS Government Securities Fund     10%
MFS High Income Fund                5%
MFS Inflation-Adjusted Bond Fund   10%
MFS Limited Maturity Fund          10%
MFS Research Bond Fund             17%
Specialty Funds:                    4%
MFS Absolute Return Fund            2%
MFS Commodity Strategy Fund         1%
MFS Global Real Estate Fund         1%
International Stock Funds:          8%
MFS International Growth Fund       2%
MFS International Value Fund        2%
MFS Research International Fund     4%
U.S. Stock Funds:                  28%
MFS Growth Fund                     6%
MFS Mid Cap Growth Fund             4%
MFS Mid Cap Value Fund              4%
MFS New Discovery Fund              1%
MFS New Discovery Value Fund        1%
MFS Research Fund                   6%
MFS Value Fund                      6%

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 and underlying funds 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, or 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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.

Commodity Risk:  The value of commodities may be more volatile than the value of
equity securities or debt instruments and their value may be affected by changes
in overall market movements, commodity index volatility, changes in interest
rates, or factors affecting a particular industry or commodity. The price of a
commodity may be affected by demand/supply imbalances in the market for the
commodity.

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; property
tax rates, 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.

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.

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 six-month period ended June 30, 2012 was 4.93%. During
the period(s) shown in the bar chart, the highest quarterly return was 10.76%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (9.28)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Conservative Allocation Fund	Label		1 Year	5 Years	Since Inception	Inception Date
A	A Shares Returns Before Taxes		(3.46%)	3.27%	4.82%	Jun. 28, 2002
B	B Shares Returns Before Taxes		(2.33%)	3.43%	4.89%	Jun. 28, 2002
C	C Shares Returns Before Taxes		0.64%	3.78%	4.77%	Jun. 28, 2002
I	I Shares Returns Before Taxes		2.65%	4.81%	5.82%	Jun. 28, 2002
529A	529A Shares Returns Before Taxes		(3.53%)	3.14%	4.63%	Jun. 28, 2002
529B	529B Shares Returns Before Taxes		(2.34%)	3.30%	4.69%	Jun. 28, 2002
529C	529C Shares Returns Before Taxes		0.64%	3.64%	4.58%	Jun. 28, 2002
R1	R1 Shares Returns Before Taxes		1.66%	3.74%	4.68%	Jun. 28, 2002
R2	R2 Shares Returns Before Taxes		2.22%	4.27%	5.16%	Jun. 28, 2002
R3	R3 Shares Returns Before Taxes		2.36%	4.51%	5.47%	Jun. 28, 2002
R4	R4 Shares Returns Before Taxes		2.75%	4.80%	5.77%	Jun. 28, 2002
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions		(4.33%)	2.23%	3.93%	Jun. 28, 2002
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares		(2.16%)	2.25%	3.70%	Jun. 28, 2002
Barclays U.S. Aggregate Bond Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Aggregate Bond Index		7.84%	6.50%	5.64%	Jun. 28, 2002
MFS Conservative Allocation Fund Blended Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Conservative Allocation Fund Blended Index	[1]	4.58%	3.81%	5.43%	Jun. 28, 2002

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

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

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

[1] The MFS Conservative Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (28%) Standard & Poor's 500 Stock Index; (8%) MSCI EAFE (Europe, Australasia, Far East) Index; (1%) The Dow Jones-UBS Commodity Index; (1%) FTSE EPRA/NAREIT Developed Real Estate Index; and (62%) Barclays U.S. Aggregate Bond Index.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Summary of Key Information
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the fund is to seek a high level of total return consistent with a moderate level of risk relative to the other MFS Asset Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth Allocation Fund, and MFS Aggressive Growth Allocation Fund.)
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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 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 6% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	6.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is designed to provide diversification among different asset classes by investing its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's investment adviser), referred to as underlying funds. The underlying funds are selected following a two stage asset allocation process. The first stage is a strategic asset allocation to determine the percentage of the fund's assets to be invested in the general asset classes of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an allocation to underlying funds that have less traditional investment strategies that MFS believes provide diversification benefits when added to a portfolio consisting of stock and bond funds (referred to as Specialty Funds). The second stage involves the actual selection of underlying funds to represent the asset classes based on underlying fund classifications, historical risk, performance, and other factors. Within the stock fund allocations, MFS seeks to diversify globally (by including domestic and international underlying funds), in terms of market capitalization (by including large, mid, and small capitalization underlying funds), and by style (by including both growth and value underlying funds). Within the bond fund allocation, MFS includes underlying funds with varying degrees of interest rate and credit exposure. As of September 28, 2012, the fund's target allocation among asset classes and the underlying funds was: Bond Funds:                             40% MFS Emerging Markets Debt Fund           3% MFS Global Bond Fund                     5% MFS Government Securities Fund          10% MFS High Income Fund                     5% MFS Inflation-Adjusted Bond Fund         5% MFS Research Bond Fund                  12% Specialty Funds:                         6% MFS Absolute Return Fund                 1% MFS Commodity Strategy Fund              3% MFS Global Real Estate Fund              2% International Stock Funds:              13% MFS International Growth Fund            3% MFS International New Discovery Fund     1% MFS International Value Fund             3% MFS Research International Fund          6% U.S. Stock Funds:                       41% MFS Growth Fund                          8% MFS Mid Cap Growth Fund                  7% MFS Mid Cap Value Fund                   7% MFS New Discovery Fund                 1.5% MFS New Discovery Value Fund           1.5% MFS Research Fund                        8% MFS Value Fund                           8%
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 and underlying funds 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. 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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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. 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, or 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. 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. Commodity Risk:  The value of commodities may be more volatile than the value of equity securities or debt instruments and their value may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The price of a commodity may be affected by demand/supply imbalances in the market for the commodity. 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; property tax rates, 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 six-month period ended June 30, 2012 was 5.90%. During the period(s) shown in the bar chart, the highest quarterly return was 13.80% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (15.13)% (for the calendar quarter ended December 31, 2008).
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, 2011)
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | Standard & Poor's 500 Stock Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
1 Year	rr_AverageAnnualReturnYear01	2.11%
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.59%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | MFS Moderate Allocation Fund Blended Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Moderate Allocation Fund Blended Index	[1]
1 Year	rr_AverageAnnualReturnYear01	2.22%
5 Years	rr_AverageAnnualReturnYear05	2.30%
Since Inception	rr_AverageAnnualReturnSinceInception	5.37%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[2]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.09%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.09%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	680
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	902
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,141
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,827
Annual Return 2003	rr_AnnualReturn2003	18.95%
Annual Return 2004	rr_AnnualReturn2004	10.59%
Annual Return 2005	rr_AnnualReturn2005	5.12%
Annual Return 2006	rr_AnnualReturn2006	10.26%
Annual Return 2007	rr_AnnualReturn2007	8.26%
Annual Return 2008	rr_AnnualReturn2008	(26.04%)
Annual Return 2009	rr_AnnualReturn2009	27.14%
Annual Return 2010	rr_AnnualReturn2010	14.53%
Annual Return 2011	rr_AnnualReturn2011	0.29%
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	5.90%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	13.80%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	the lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(15.13%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.48%)
5 Years	rr_AverageAnnualReturnYear05	1.96%
Since Inception	rr_AverageAnnualReturnSinceInception	5.18%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(6.22%)
5 Years	rr_AverageAnnualReturnYear05	1.03%
Since Inception	rr_AverageAnnualReturnSinceInception	4.38%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(3.44%)
5 Years	rr_AverageAnnualReturnYear05	1.22%
Since Inception	rr_AverageAnnualReturnSinceInception	4.11%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.84%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.84%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	587
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	879
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,196
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,962
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	1,962
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.33%)
5 Years	rr_AverageAnnualReturnYear05	2.09%
Since Inception	rr_AverageAnnualReturnSinceInception	5.26%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.84%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	(1.42%)
5 Years	rr_AverageAnnualReturnYear05	2.45%
Since Inception	rr_AverageAnnualReturnSinceInception	5.14%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.84%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	0.53%
5 Years	rr_AverageAnnualReturnYear05	3.48%
Since Inception	rr_AverageAnnualReturnSinceInception	6.21%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529A
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.19%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.14%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	685
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	926
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,187
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,931
Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.55%)
5 Years	rr_AverageAnnualReturnYear05	1.83%
Since Inception	rr_AverageAnnualReturnSinceInception	5.00%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.94%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	592
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	904
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,242
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,066
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	192
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	604
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,042
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,066
Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.41%)
5 Years	rr_AverageAnnualReturnYear05	1.96%
Since Inception	rr_AverageAnnualReturnSinceInception	5.07%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.94%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.89%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	292
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	604
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,042
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,260
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	192
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	604
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,042
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,260
Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(1.50%)
5 Years	rr_AverageAnnualReturnYear05	2.30%
Since Inception	rr_AverageAnnualReturnSinceInception	4.95%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.84%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	(0.53%)
5 Years	rr_AverageAnnualReturnYear05	2.42%
Since Inception	rr_AverageAnnualReturnSinceInception	5.04%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.34%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	(0.04%)
5 Years	rr_AverageAnnualReturnYear05	2.92%
Since Inception	rr_AverageAnnualReturnSinceInception	5.54%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.09%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	0.30%
5 Years	rr_AverageAnnualReturnYear05	3.19%
Since Inception	rr_AverageAnnualReturnSinceInception	5.85%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.09%
Acquired (Underlying) Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.84%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	none	[3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	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
1 Year	rr_AverageAnnualReturnYear01	0.53%
5 Years	rr_AverageAnnualReturnYear05	3.45%
Since Inception	rr_AverageAnnualReturnSinceInception	6.13%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 28, 2002

[1] The MFS Moderate Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (41%) Standard & Poor's 500 Stock Index; (13%) MSCI EAFE (Europe, Australasia, Far East) Index; (3%) The Dow Jones-UBS Commodity Index; (2%) FTSE EPRA/NAREIT Developed Real Estate Index ; and (41%) Barclays U.S. Aggregate Bond Index.

[2] 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.

[3] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	May 31, 2012
Registrant Name	dei_EntityRegistrantName	MFS SERIES TRUST X
Central Index Key	dei_EntityCentralIndexKey	0000783740
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Sep. 27, 2012
Document Effective Date	dei_DocumentEffectiveDate	Sep. 28, 2012
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACFX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACBX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACVX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACIX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ECLAX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EBCAX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ECACX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACKX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCARX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACNX
MFS Conservative Allocation Fund (Prospectus Summary) | MFS Conservative Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MACJX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAMAX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMABX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMACX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MMAIX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EAMDX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EBMDX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ECMAX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAMFX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MARRX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAMHX
MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAMJX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MBGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGWIX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EAGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EBGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ECGWX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAGMX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGALX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAGEX
MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAGJX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAAGX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MBAGX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MCAGX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MIAGX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EAGTX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	EBAAX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ECAAX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAAFX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAWAX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAAHX
MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MAALX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNAX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNBX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNCX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNIX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNRX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNSX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNTX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNUX
MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return Fund | R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MRNVX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMAX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMBX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMCX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMIX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMRX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMFX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMGX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMHX
MFS Emerging Markets Equity Fund (Prospectus Summary) | MFS Emerging Markets Equity Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MEMJX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBAX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBBX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBDX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBJX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBKX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBLX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBMX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBNX
MFS Global Bond Fund (Prospectus Summary) | MFS Global Bond Fund | R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGBOX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIDX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIFX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIGX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIJX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIEX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIMX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDINX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIOX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIKX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDIHX
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MDITX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRAX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRBX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRCX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MQGIX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRRX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRQX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRTX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRVX
MFS International Growth Fund (Prospectus Summary) | MFS International Growth Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGRDX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGIAX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGIBX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MGICX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINIX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINRX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINFX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINGX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINHX
MFS International Value Fund (Prospectus Summary) | MFS International Value Fund | Class R5
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	MINJX

XML

MFS Growth Allocation Fund (Prospectus Summary) | MFS Growth Allocation Fund

Summary of Key Information

Investment Objective

The investment objective of the fund is to seek a high level of total return
consistent with a greater than moderate level of risk relative to the other MFS
Asset Allocation Funds.  (The MFS Asset Allocation Funds currently include the
MFS Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth
Allocation Fund, and MFS Aggressive Growth Allocation Fund.)

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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 of
the fund's statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Growth Allocation Fund	A		B	C	I	529A	529B	529C	R1	R2	R3	R4
Shareholder Fees Column [Text]	A		B	C	I	529A	529B	529C	ALL R	ALL R	ALL R	ALL R
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	5.75%	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	4.00%	1.00%	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 Growth Allocation Fund		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Operating Expenses Column [Text]		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Management Fee		none	none	none	none	none	none	none	none	none	none	none
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	0.25%	1.00%	1.00%	1.00%	0.50%	0.25%	none
Other Expenses		0.11%	0.11%	0.11%	0.11%	0.21%	0.21%	0.21%	0.11%	0.11%	0.11%	0.11%
Acquired (Underlying) Fund Fees and Expenses		0.81%	0.81%	0.81%	0.81%	0.81%	0.81%	0.81%	0.81%	0.81%	0.81%	0.81%
Total Annual Fund Operating Expenses		1.17%	1.92%	1.92%	0.92%	1.27%	2.02%	2.02%	1.92%	1.42%	1.17%	0.92%
Fee Reductions and/or Expense Reimbursements	[1]	none	none	none	none	(0.05%)	(0.05%)	(0.05%)	none	none	none	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expens Reimbursements		1.17%	1.92%	1.92%	0.92%	1.22%	1.97%	1.97%	1.92%	1.42%	1.17%	0.92%

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 Growth Allocation Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	687	925	1,182	1,914
B	Class B Shares assuming redemption at end of period	595	903	1,237	2,048
C	Class C Shares assuming redemption at end of period	295	603	1,037	2,243
I	Class I Shares	94	293	509	1,131
529A	Class 529A Shares	692	950	1,227	2,017
529B	Class 529B Shares assuming redemption at end of period	600	929	1,283	2,151
529C	Class 529C Shares assuming redemption at end of period	300	629	1,083	2,344
R1	Class R1 Shares	195	603	1,037	2,243
R2	Class R2 Shares	145	449	776	1,702
R3	Class R3 Shares	119	372	644	1,420
R4	Class R4 Shares	94	293	509	1,131

Expense Example, No Redemption MFS Growth Allocation Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	195	603	1,037	2,048
C	Class C Shares assuming no redemption at end of period	195	603	1,037	2,243
529B	Class 529B Shares assuming no redemption at end period	200	629	1,083	2,151
529C	Class 529C Shares assuming no redemption at end of period	200	629	1,083	2,344

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 7% of the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification among different asset classes by
investing its assets in other mutual funds advised by MFS (Massachusetts
Financial Services Company, the fund's investment adviser), referred to as
underlying funds. The underlying funds are selected following a two stage asset
allocation process. The first stage is a strategic asset allocation to determine
the percentage of the fund's assets to be invested in the general asset classes
of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an
allocation to underlying funds that have less traditional investment strategies
that MFS believes provide diversification benefits when added to a portfolio
consisting of stock and bond funds (referred to as Specialty Funds). The second
stage involves the actual selection of underlying funds to represent the asset
classes based on underlying fund classifications, historical risk, performance,
and other factors. Within the stock fund allocations, MFS seeks to diversify
globally (by including domestic and international underlying funds), in terms of
market capitalization (by including large, mid, and small capitalization
underlying funds), and by style (by including both growth and value underlying
funds). Within the bond fund allocation, MFS includes underlying funds with
varying degrees of interest rate and credit exposure.

As of September 28, 2012, the fund's target allocation among asset classes and
the underlying funds was:

Bond Funds:                            20%
MFS Emerging Markets Debt Fund          3%
MFS Global Bond Fund                    4%
MFS High Income Fund                    5%
MFS Inflation-Adjusted Bond Fund        5%
MFS Research Bond Fund                  3%
Specialty Funds:                        8%
MFS Absolute Return Fund                1%
MFS Commodity Strategy Fund             4%
MFS Global Real Estate Fund             3%
International Stock Funds:             20%
MFS Emerging Markets Equity Fund        1%
MFS International Growth Fund           5%
MFS International New Discovery Fund    2%
MFS International Value Fund            5%
MFS Research International Fund         7%
U.S. Stock Funds:                      52%
MFS Growth Fund                        11%
MFS Mid Cap Growth Fund                 9%
MFS Mid Cap Value Fund                  9%
MFS New Discovery Fund                  2%
MFS New Discovery Value Fund            2%
MFS Research Fund                       8%
MFS Value Fund                         11%

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 and underlying funds 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.

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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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.

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, or 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.

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.

Commodity Risk:  The value of commodities may be more volatile than the value of
equity securities or debt instruments and their value may be affected by changes
in overall market movements, commodity index volatility, changes in interest
rates, or factors affecting a particular industry or commodity. The price of a
commodity may be affected by demand/supply imbalances in the market for the
commodity.

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; property
tax rates, 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 six-month period ended June 30, 2012 was 6.92%. During
the period(s) shown in the bar chart, the highest quarterly return was 17.14%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (20.20)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Growth Allocation Fund	Label		1 Year	5 Years	Since Inception	Inception Date
A	A Shares Returns Before Taxes		(7.94%)	0.30%	5.28%	Jun. 28, 2002
B	B Shares Returns Before Taxes		(6.90%)	0.44%	5.34%	Jun. 28, 2002
C	C Shares Returns Before Taxes		(4.06%)	0.78%	5.22%	Jun. 28, 2002
I	I Shares Returns Before Taxes		(2.01%)	1.80%	6.28%	Jun. 28, 2002
529A	529A Shares Returns Before Taxes		(7.96%)	0.18%	5.08%	Jun. 28, 2002
529B	529B Shares Returns Before Taxes		(6.88%)	0.31%	5.13%	Jun. 28, 2002
529C	529C Shares Returns Before Taxes		(4.10%)	0.65%	5.02%	Jun. 28, 2002
R1	R1 Shares Returns Before Taxes		(3.00%)	0.77%	5.13%	Jun. 28, 2002
R2	R2 Shares Returns Before Taxes		(2.58%)	1.25%	5.61%	Jun. 28, 2002
R3	R3 Shares Returns Before Taxes		(2.33%)	1.51%	5.91%	Jun. 28, 2002
R4	R4 Shares Returns Before Taxes		(2.09%)	1.79%	6.22%	Jun. 28, 2002
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions		(8.46%)	(0.49%)	4.61%	Jun. 28, 2002
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares		(4.96%)	(0.05%)	4.33%	Jun. 28, 2002
Standard & Poor's 500 Stock Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index		2.11%	(0.25%)	4.59%	Jun. 28, 2002
MFS Growth Allocation Fund Blended Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Growth Allocation Fund Blended Index	[1]	(0.24%)	0.58%	5.33%	Jun. 28, 2002

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

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

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

[1] The MFS Growth Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (52%) Standard & Poor's 500 Stock Index; (20%) MSCI EAFE (Europe, Australasia, Far East) Index; (4%) The Dow Jones-UBS Commodity Index; (3%) FTSE EPRA/NAREIT Developed Real Estate Index; and (21%) Barclays U.S. Aggregate Bond Index.

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MFS International Growth Fund (Prospectus Summary) | MFS International Growth 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-16 of
the fund's statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS International Growth Fund	A		B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Shareholder Fees Column [Text]	A		B	C	I	ALL R	ALL R	ALL R	ALL R	ALL R
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 International Growth Fund	A	B	C	I	Class R1	Class R2	Class R3	Class R4	Class R5
Operating Expenses Column [Text]	A	B	C	I	R1	R2	R3	R4	R5
Management Fee	0.85%	0.85%	0.85%	0.85%	0.85%	0.85%	0.85%	0.85%	0.85%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses	0.27%	0.27%	0.27%	0.27%	0.27%	0.27%	0.27%	0.27%	0.17%
Total Annual Fund Operating Expenses	1.37%	2.12%	2.12%	1.12%	2.12%	1.62%	1.37%	1.12%	1.02%

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 International Growth Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	706	984	1,282	2,127
B	Class B Shares assuming redemption at end of period	615	964	1,339	2,261
C	Class C Shares assuming redemption at end of period	315	664	1,139	2,452
I	Class I Shares	114	356	617	1,363
Class R1	Class R1 Shares	215	664	1,139	2,452
Class R2	Class R2 Shares	165	511	881	1,922
Class R3	Class R3 Shares	139	434	750	1,646
Class R4	Class R4 Shares	114	356	617	1,363
Class R5	Class R5 Shares	104	325	563	1,248

Expense Example, No Redemption MFS International Growth Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	215	664	1,139	2,261
C	Class C Shares assuming no redemption at end of period	215	664	1,139	2,452

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 39% 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 foreign equity securities,
including emerging market equity securities. Equity securities include common
stocks, preferred stocks, securities convertible into stocks, and depositary
receipts for those securities.

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 focuses on investing the fund's assets in the stocks of companies it
believes to have above average earnings growth potential compared to other
companies (growth companies).
  
MFS may invest the fund's assets in companies of any size.
  
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.
  
Foreign and Emerging Markets Risk: Exposure to foreign markets, especially
emerging markets, through issuers or currencies can involve additional risks
relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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, or 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.
  
Growth Company Risk: The stocks of growth companies can be more sensitive to
the company's earnings and more volatile than the market in general.
  
Investment Selection Risk: MFS' investment analysis and its selection of
investments may not produce the intended results and/or can lead to an
investment focus that results in the fund underperforming other funds with
similar investment strategies and/or underperforming the markets in which the
fund invests.
  
Counterparty and Third Party Risk: Transactions involving a counterparty or
third party other than the issuer of the instrument are subject to the credit
risk of the counterparty or third party, and to the counterparty's or third
party's ability to perform in accordance with the terms of the transaction.
  
Liquidity Risk: It may not be possible to sell certain investments, types of
investments, and/or segments of the market at any particular time or at an
acceptable price.

Performance Information

The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in the
fund's performance over time and how the fund's performance over time compares
with that of a broad measure of market performance.
  
The fund's past performance (before and after taxes) does not necessarily
indicate how the fund will perform in the future. Updated performance is
available online at mfs.com or by calling 1-800-225-2606.

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

Class A Bar Chart.

The total return for the six-month period ended June 30, 2012 was 6.25%. During
the period(s) shown in the bar chart, the highest quarterly return was 23.27%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (19.64)% (for the calendar quarter ended September 30, 2011).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS International Growth Fund	Label	1 Year	5 Years	10 Years
A	A Shares Returns Before Taxes	(15.97%)	(1.58%)	6.39%
B	B Shares Returns Before Taxes	(15.03%)	(1.47%)	6.49%
C	C Shares Returns Before Taxes	(12.42%)	(1.12%)	6.33%
I	I Shares Returns Before Taxes	(10.62%)	(0.12%)	7.63%
Class R1	R1 Shares Returns Before Taxes	(11.52%)	(1.12%)	6.33%
Class R2	R2 Shares Returns Before Taxes	(11.06%)	(0.62%)	6.87%
Class R3	R3 Shares Returns Before Taxes	(10.80%)	(0.37%)	7.14%
Class R4	R4 Shares Returns Before Taxes	(10.63%)	(0.13%)	7.40%
Class R5	R5 Shares Returns Before Taxes	(10.70%)	(0.22%)	7.29%
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions	(15.96%)	(2.00%)	5.94%
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares	(10.11%)	(1.31%)	5.57%
MSCI All Country World (ex-US) Growth Index (gross div)	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI All Country World (ex-US) Growth Index (gross div)	(13.93%)	(1.84%)	5.94%

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

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

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 28, 2012
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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 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 8% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	8.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund is designed to provide diversification within the international asset class by investing the majority of its assets in other mutual funds advised by MFS (Massachusetts Financial Services Company, the fund's Investment adviser), referred to as underlying funds. The underlying funds are selected based on underlying fund classifications, historical risk, performance, and other factors. MFS seeks to diversify the fund's investments in terms of market capitalization (by including large, mid, and/or small cap underlying funds), by style (by including both growth and value underlying funds), and by geographic region (by including developed and emerging market underlying funds). However, MFS may invest a relatively large percentage of the underlying funds' assets in a single country, a small number of countries, or a particular geographic region. As of September 28, 2012, the fund's target allocation among underlying funds was:    MFS Emerging Markets Equity Fund       10% MFS International Growth Fund          25% MFS International New Discovery Fund   10% MFS International Value Fund           25% MFS Research International Fund        30%
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 and underlying funds 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.    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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical or 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, or 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.    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. The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-225-2606
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	mfs.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Class A Bar Chart.
Bar Chart Narrative [Text Block]	rr_BarChartNarrativeTextBlock	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total return for the six-month period ended June 30, 2012 was 5.68%.  During the period(s) shown in the bar chart, the highest quarterly return was 23.90% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (19.72)% (for the calendar quarter ended September 30, 2008).
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, 2011)
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | MSCI All Country World (ex-US) Growth Index (gross div)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI All Country World (ex-US) Index (gross div)
1 Year	rr_AverageAnnualReturnYear01	(13.33%)
5 Years	rr_AverageAnnualReturnYear05	(2.48%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.98%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	A
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[1]
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.35%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.32%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	702
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	975
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,269
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,103
Annual Return 2005	rr_AnnualReturn2005	16.65%
Annual Return 2006	rr_AnnualReturn2006	27.11%
Annual Return 2007	rr_AnnualReturn2007	12.77%
Annual Return 2008	rr_AnnualReturn2008	(40.25%)
Annual Return 2009	rr_AnnualReturn2009	34.21%
Annual Return 2010	rr_AnnualReturn2010	13.20%
Annual Return 2011	rr_AnnualReturn2011	(9.40%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The total return for the six-month period ended
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	5.68%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	the highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	23.90%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	the lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(19.72%)
Label	rr_AverageAnnualReturnLabel	A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(14.61%)
5 Years	rr_AverageAnnualReturnYear05	(2.65%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.65%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(14.72%)
5 Years	rr_AverageAnnualReturnYear05	(3.29%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.86%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	A Shares Returns After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(9.34%)
5 Years	rr_AverageAnnualReturnYear05	(2.35%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.70%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.07%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	610
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	955
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,326
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,237
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	210
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	655
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,126
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,237
Label	rr_AverageAnnualReturnLabel	B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.71%)
5 Years	rr_AverageAnnualReturnYear05	(2.52%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.79%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.07%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	310
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	655
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,126
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,429
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	210
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	655
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,126
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,429
Label	rr_AverageAnnualReturnLabel	C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.97%)
5 Years	rr_AverageAnnualReturnYear05	(2.18%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.78%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | I
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	I
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	I
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.07%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	109
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	347
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	603
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,338
Label	rr_AverageAnnualReturnLabel	I Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.17%)
5 Years	rr_AverageAnnualReturnYear05	(1.18%)
Since Inception	rr_AverageAnnualReturnSinceInception	6.85%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529A
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529A
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529A
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.23%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.45%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.37%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	706
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	992
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,307
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,197
Label	rr_AverageAnnualReturnLabel	529A Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(14.71%)
5 Years	rr_AverageAnnualReturnYear05	(2.79%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.45%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529B
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529B
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_MaximumDeferredSalesChargeOverOfferingPrice	4.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529B
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.23%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.20%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.12%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	615
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	972
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,365
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,331
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	215
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	672
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,165
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,331
Label	rr_AverageAnnualReturnLabel	529B Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.71%)
5 Years	rr_AverageAnnualReturnYear05	(2.66%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.60%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | 529C
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	529C
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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	529C
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.23%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.20%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.12%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	315
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	672
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,165
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,521
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	215
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	672
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,165
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,521
Label	rr_AverageAnnualReturnLabel	529C Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(11.10%)
5 Years	rr_AverageAnnualReturnYear05	(2.30%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.61%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R1
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R1
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	2.07%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	210
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	655
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,126
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,429
Label	rr_AverageAnnualReturnLabel	R1 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(10.10%)
5 Years	rr_AverageAnnualReturnYear05	(2.21%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.71%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R2
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R2
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.60%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.57%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	160
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	502
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	868
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,898
Label	rr_AverageAnnualReturnLabel	R2 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.70%)
5 Years	rr_AverageAnnualReturnYear05	(1.72%)
Since Inception	rr_AverageAnnualReturnSinceInception	6.22%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R3
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R3
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.35%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.32%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	134
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	425
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	737
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,621
Label	rr_AverageAnnualReturnLabel	R3 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.43%)
5 Years	rr_AverageAnnualReturnYear05	(1.48%)
Since Inception	rr_AverageAnnualReturnSinceInception	6.49%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004
MFS International Diversification Fund (Prospectus Summary) | MFS International Diversification Fund | R4
Risk Return [Abstract]	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	ALL R
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_MaximumDeferredSalesChargeOverOfferingPrice	none
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	R4
Management Fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.13%
Acquired (Underlying) Fund	rr_AcquiredFundFeesAndExpensesOverAssets	0.97%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.10%
Fee Reductions and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.03%)	[2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.07%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2013-09-30
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	109
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	347
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	603
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,338
Label	rr_AverageAnnualReturnLabel	R4 Shares Returns Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(9.13%)
5 Years	rr_AverageAnnualReturnYear05	(1.24%)
Since Inception	rr_AverageAnnualReturnSinceInception	6.78%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 30, 2004

[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] Effective June 1, 2012, Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding program management fees, management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, such that "Other Expenses" do not exceed 0.10% of the fund's average daily net assets annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013. In addition, the fund's distributor, MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2014, unless MFS Fund Distributors, Inc. elects to extend the waiver.

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MFS Absolute Return Fund (Prospectus Summary) | MFS Absolute Return 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. Expenses for Class A, Class B, Class C, Class I,
Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect
current fee arrangements. The annual fund operating expenses for Class R5 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 11 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 Absolute Return Fund	A		B	C	I	R1	R2	R3	R4	R5
Shareholder Fees Column [Text]	A		B	C	I	ALL R	ALL R	ALL R	ALL R	ALL R
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 Absolute Return Fund		A	B	C	I	R1	R2	R3	R4	R5
Operating Expenses Column [Text]		A	B	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%	0.65%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	1.00%	0.50%	0.25%	none	none
Other Expenses		0.64%	0.64%	0.64%	0.64%	0.64%	0.64%	0.64%	0.64%	0.64%
Total Annual Fund Operating Expenses		1.54%	2.29%	2.29%	1.29%	2.29%	1.79%	1.54%	1.29%	1.29%
Fee Reductions and/or Expense Reimbursements	[1]	(0.40%)	(0.40%)	(0.40%)	(0.40%)	(0.40%)	(0.40%)	(0.40%)	(0.40%)	(0.40%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.14%	1.89%	1.89%	0.89%	1.89%	1.39%	1.14%	0.89%	0.89%

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 Absolute Return Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	586	901	1,239	2,190
B	Class B Shares assuming redemption at end of period	592	977	1,389	2,406
C	Class C Shares assuming redemption at end of period	292	677	1,189	2,595
I	Class I Shares	91	369	669	1,521
R1	Class R1 Shares	192	677	1,189	2,595
R2	Class R2 Shares	142	524	932	2,072
R3	Class R3 Shares	116	447	802	1,801
R4	Class R4 Shares	91	369	669	1,521
R5	Class R5 Shares	91	369	669	1,521

Expense Example, No Redemption MFS Absolute Return Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	192	677	1,189	2,406
C	Class C Shares assuming no redemption at end of period	192	677	1,189	2,595

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when shares are
held in a taxable account. These transaction costs, which are not reflected in
"Annual Fund Operating Expenses" or in the "Example," affect the fund's performance.  
During the most recent fiscal year, the fund's portfolio turnover rate was 10% of
the average value of its portfolio.

Principal Investment Strategies

In managing the fund, MFS (Massachusetts Financial Services Company, the fund's
investment adviser) employs an absolute return investment approach, which means
the fund seeks to earn a positive return regardless of market conditions. As
a result, if this strategy is successful, it is expected that the fund will
outperform the general equity market during periods of flat or negative market
performance, will underperform during periods of strong positive market
performance, and will typically produce less volatile returns than the general
equity market.
  
MFS seeks to achieve the fund's objective by generating returns from a
combination of (1) individual security selection of primarily debt instruments
and (2) a tactical asset allocation overlay primarily using derivative
instruments to manage the fund's exposure to asset classes, markets and
currencies. Derivatives include futures, forward contracts, options, structured
securities, inverse floating rate instruments, and swaps.

The fund's performance may not be correlated with the performance of the asset
classes, markets or currencies represented by the individual investments
selected by MFS.
  
Individual Security Selection:  In selecting direct investments for the fund,
MFS normally invests the fund's assets primarily in debt instruments.
  
Debt instruments include corporate bonds, U.S. Government securities,
asset-backed securities, municipal instruments, foreign government securities,
inflation-adjusted bonds, and other obligations to repay money borrowed.
  
Of the fund's investments in debt instruments, MFS generally invests
substantially all of these investments in investment grade debt instruments.
  
While MFS may invest the fund's assets in debt instruments of any effective
maturity, MFS generally focuses on short and intermediate term debt instruments.
  
MFS may invest the fund's assets in U.S. and foreign securities, including
emerging market securities.
  
While MFS may use derivatives for any investment purpose, to the extent MFS uses
derivatives as part of its individual security selection process, 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.

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.
  
Tactical Asset Allocation Overlay:  MFS employs a top-down tactical asset
allocation process to adjust the fund's exposure to asset classes, markets
and currencies based on its assessment of the relative attractiveness of
such asset classes, markets and currencies. MFS manages the fund's exposure
to asset classes, markets and currencies primarily through the use of
derivative instruments based on its proprietary quantitative models.
  
In managing the tactical overlay, MFS may increase or decrease the fund's
exposure to asset classes, markets and/or currencies resulting from MFS'
individual security selection based on MFS' assessment of the risk/return
potential of such asset classes, markets and/or currencies. MFS may also expose
the fund to asset classes, markets and/or currencies in which its individual
security selection has resulted in no or little exposure (e.g., commodity-related
investments, real estate-related investments, equity securities, inflation-adjusted
debt instruments). After taking into account the tactical overlay, the fund's
exposure to certain asset classes in which its individual security selection
has resulted in no or little exposure will normally fall within the following
ranges:
  
Asset Class                           Range  
U.S. and foreign equity securities      ±15%
Inflation-adjusted debt instruments     ±10%
Commodity-related investments           ±10%
Real estate-related investments         ± 5%
  
After taking into account the tactical overlay, the fund's exposure to the less
than investment grade quality debt instrument (lower quality debt instrument)
and long term debt instrument asset classes may at times be significant, and the
fund may have significant exposure to issuers in a single country, a small
number of countries, or a particular geographic region.

MFS may adjust the fund's net exposure to asset classes, markets and/or
currencies by taking net short positions in an asset class, market or currency
if MFS believes the risk/return potential of such asset class, market or
currency is unattractive.  Alternatively, MFS may cause the fund to take net
long positions in an asset class, market or currency if MFS believes such asset
class, market or currency appears attractive.

MFS may also use derivatives to seek to limit the fund's exposure to certain
extreme market events.
  
MFS' tactical allocation process for the fund will typically make extensive use
of derivatives.

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, its assessment of the risk/return potential of asset
classes, markets and currencies, and its adjustments to the fund's exposure to
asset classes, markets, and currencies through the use of derivatives 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.
  
Investment Strategy Risk:  The fund's strategy to manage its exposure to asset
classes, markets, and currencies may not produce the intended results. In
addition, the strategies MFS may implement to limit the fund's exposure to
certain extreme market events may not work as intended, and the costs associated
with such strategies will reduce the fund's returns.

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, or 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.
  
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.
  
Foreign and Emerging Markets Risk: Exposure to foreign markets, especially
emerging markets, through issuers or currencies can involve additional risks
relating to market, economic, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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, or 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.

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.
  
Commodity Risk:  The value of commodities may be more volatile than the value of
equity securities or debt instruments and their value may be affected by changes
in overall market movements, commodity index volatility, changes in interest
rates, or factors affecting a particular industry or commodity. The price of
a commodity may be affected by demand/supply imbalances in the market for the
commodity.
  
Tax Risk:  In order to qualify as a regulated investment company (RIC) under
the Internal Revenue Code of 1986, as amended, the fund must meet certain
requirements regarding the source of its income, the diversification of its
assets, and the distribution of its income. If the fund were to fail to
qualify as a RIC and became subject to federal income tax, shareholders of
the fund would be subject to the risk of diminished returns.
  
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; property tax rates, 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.

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 are not included because the fund has not
had a full calendar year of operations.

[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 1.15% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 1.90% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.90% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.40% of the fund's average daily net assets annually for Class R2 shares, and 0.89% 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 September 30, 2013.

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MFS Aggressive Growth Allocation Fund (Prospectus Summary) | MFS Aggressive Growth Allocation Fund

Summary of Key Information

Investment Objective

The investment objective of the fund is to seek a high level of total return
consistent with an aggressive level of risk relative to the other MFS Asset
Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS
Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth
Allocation Fund, and MFS Aggressive Growth Allocation Fund.)

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 9 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 of
the fund's statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Aggressive Growth Allocation Fund	A		B	C	I	529A	529B	529C	R1	R2	R3	R4
Shareholder Fees Column [Text]	A		B	C	I	529A	529B	529C	ALL R	ALL R	ALL R	ALL R
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	5.75%	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	4.00%	1.00%	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 Aggressive Growth Allocation Fund		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Operating Expenses Column [Text]		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Management Fee		none	none	none	none	none	none	none	none	none	none	none
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	0.25%	1.00%	1.00%	1.00%	0.50%		none
Other Expenses		0.15%	0.15%	0.15%	0.15%	0.25%	0.25%	0.25%	0.15%	0.15%	0.15%	0.15%
Acquired (Underlying) Fund Fees and Expenses		0.86%	0.86%	0.86%	0.86%	0.86%	0.86%	0.86%	0.86%	0.86%	0.86%	0.86%
Total Annual Fund Operating Expenses		1.26%	2.01%	2.01%	1.01%	1.36%	2.11%	2.11%	2.01%	1.51%	1.26%	1.01%
Fee Reductions and/or Expense Reimbursements	[1]	(0.02%)	(0.02%)	(0.02%)	(0.02%)	(0.07%)	(0.07%)	(0.07%)	(0.02%)	(0.02%)	(0.02%)	(0.02%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.24%	1.99%	1.99%	0.99%	1.29%	2.04%	2.04%	1.99%	1.49%	1.24%	0.99%

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 Aggressive Growth Allocation Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	694	950	1,225	2,008
B	Class B Shares assuming redemption at end of period	602	929	1,281	2,143
C	Class C Shares assuming redemption at end of period	302	629	1,081	2,336
I	Class I Shares	101	320	556	1,234
529A	Class 529A Shares	699	974	1,271	2,110
529B	Class 529B Shares assuming redemption at end of period	607	954	1,328	2,245
529C	Class 529C Shares assuming redemption at end of period	307	654	1,128	2,436
R1	Class R1 Shares	202	629	1,081	2,336
R2	Class R2 Shares	152	475	822	1,800
R3	Class R3 Shares	126	398	690	1,521
R4	Class R4 Shares	101	320	556	1,234

Expense Example, No Redemption MFS Aggressive Growth Allocation Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares no redemption at end of period	202	629	1,081	2,143
C	Class C no redemption at end of period	202	629	1,081	2,336
529B	Class 529B no redemption at end of period	207	654	1,128	2,245
529C	Class 529C no redemption at end of period	207	654	1,128	2,436

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when
shares are held in a taxable account. These transaction costs, which are not
reflected in "Annual Fund Operating Expenses" or in the "Example," affect the
fund's performance.  During the most recent fiscal year, the fund's portfolio
turnover rate was 11% of the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification among different asset classes by
investing its assets in other mutual funds advised by MFS (Massachusetts
Financial Services Company, the fund's investment adviser), referred to as
underlying funds. The underlying funds are selected following a two stage asset
allocation process. The first stage is a strategic asset allocation to determine
the percentage of the fund's assets to be invested in the general asset classes
of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an
allocation to underlying funds that have less traditional investment strategies
that MFS believes provide diversification benefits when added to a portfolio
consisting of stock and bond funds (referred to as Specialty Funds). The second
stage involves the actual selection of underlying funds to represent the asset
classes based on underlying fund classifications, historical risk, performance,
and other factors. Within the stock fund allocations, MFS seeks to diversify
globally (by including domestic and international underlying funds), in terms of
market capitalization (by including large, mid, and small capitalization
underlying funds), and by style (by including both growth and value underlying
funds).

As of September 28, 2012, the fund's target allocation among asset classes and
the underlying funds was:

Bond Funds:                              0%
Specialty Funds:                        10%
MFS Commodity Strategy Fund              5%
MFS Global Real Estate Fund              5%
International Stock Funds:              30%
MFS Emerging Markets Equity Fund         2%
MFS International Growth Fund            8%
MFS International New Discovery Fund     4%
MFS International Value Fund             8%
MFS Research International Fund          8%
U.S. Stock Funds:                       60%
MFS Growth Fund                         13%
MFS Mid Cap Growth Fund                 10%
MFS Mid Cap Value Fund                  10%
MFS New Discovery Fund                 2.5%
MFS New Discovery Value Fund           2.5%
MFS Research Fund                        9%
MFS Value Fund                          13%

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 and underlying funds 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.

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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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.
  
Commodity Risk:  The value of commodities may be more volatile than the value of
equity securities or debt instruments and their value may be affected by changes
in overall market movements, commodity index volatility, changes in interest
rates, or factors affecting a particular industry or commodity. The price of a
commodity may be affected by demand/supply imbalances in the market for the
commodity.

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;
property tax rates, 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 six-month period ended June 30, 2012 was 7.42%. During
the period(s) shown in the bar chart, the highest quarterly return was 19.81%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (24.63)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Aggressive Growth Allocation Fund	Label		1 Year	5 Years	Since Inception	Inception Date
A	A Shares Returns Before Taxes		(10.44%)	(1.29%)	4.67%	Jun. 28, 2002
B	B Shares Returns Before Taxes		(9.53%)	(1.18%)	4.77%	Jun. 28, 2002
C	C Shares Returns Before Taxes		(6.61%)	(0.82%)	4.63%	Jun. 28, 2002
I	I Shares Returns Before Taxes		(4.82%)	0.17%	5.68%	Jun. 28, 2002
529A	529A Shares Returns Before Taxes		(10.61%)	(1.43%)	4.50%	Jun. 28, 2002
529B	529B Shares Returns Before Taxes		(9.59%)	(1.32%)	4.52%	Jun. 28, 2002
529C	529C Shares Returns Before Taxes		(6.71%)	(0.96%)	4.43%	Jun. 28, 2002
R1	R1 Shares Returns Before Taxes		(5.70%)	(0.85%)	4.53%	Jun. 28, 2002
R2	R2 Shares Returns Before Taxes		(5.27%)	(0.37%)	5.02%	Jun. 28, 2002
R3	R3 Shares Returns Before Taxes		(5.00%)	(0.11%)	5.32%	Jun. 28, 2002
R4	R4 Shares Returns Before Taxes		(4.80%)	0.15%	5.61%	Jun. 28, 2002
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions		(10.68%)	(1.79%)	4.27%	Jun. 28, 2002
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares		(6.56%)	(1.18%)	3.99%	Jun. 28, 2002
Standard & Poor's 500 Stock Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index		2.11%	(0.25%)	4.59%	Jun. 28, 2002
MFS Aggressive Growth Allocation Fund Blended Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Aggressive Growth Allocation Fund Blended Index	[1]	(3.32%)	(1.25%)	4.76%	Jun. 28, 2002

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 program management fees, management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, such that "Other Expenses" do not exceed 0.13% of the fund's average daily net asset annually for each class of shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2013. In addition, MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

[1] The MFS Aggressive Growth Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (60%) Standard & Poor's 500 Stock Index; (30%) MSCI EAFE (Europe, Australasia, Far East) Index; (5%) The Dow Jones-UBS Commodity Index; and (5%) FTSE EPRA/NAREIT Developed Real Estate Index.

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MFS Moderate Allocation Fund (Prospectus Summary) | MFS Moderate Allocation Fund

Summary of Key Information

Investment Objective

The investment objective of the fund is to seek a high level of total return
consistent with a moderate level of risk relative to the other MFS Asset
Allocation Funds.  (The MFS Asset Allocation Funds currently include the MFS
Conservative Allocation Fund, MFS Moderate Allocation Fund, MFS Growth
Allocation Fund, and MFS Aggressive Growth Allocation Fund.)

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 11 of the fund's prospectus and "Waivers of Sales Charges" on page I-20 of
the fund's statement of additional information Part I.

Shareholder Fees (fees paid directly from your investment):

Shareholder Fees MFS Moderate Allocation Fund	A		B	C	I	529A	529B	529C	R1	R2	R3	R4
Shareholder Fees Column [Text]	A		B	C	I	529A	529B	529C	ALL R	ALL R	ALL R	ALL R
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	5.75%		none	none	none	5.75%	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	4.00%	1.00%	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 Moderate Allocation Fund		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Operating Expenses Column [Text]		A	B	C	I	529A	529B	529C	R1	R2	R3	R4
Management Fee		none	none	none	none	none	none	none	none	none	none	none
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none	0.25%	1.00%	1.00%	1.00%	0.50%	0.25%	none
Other Expenses		0.09%	0.09%	0.09%	0.09%	0.19%	0.19%	0.19%	0.09%	0.09%	0.09%	0.09%
Acquired (Underlying) Fund Fees and Expenses		0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%
Total Annual Fund Operating Expenses		1.09%	1.84%	1.84%	0.84%	1.19%	1.94%	1.94%	1.84%	1.34%	1.09%	0.84%
Fee Reductions and/or Expense Reimbursements	[1]	none	none	none	none	(0.05%)	(0.05%)	(0.05%)	none	none	none	none
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.09%	1.84%	1.84%	0.84%	1.14%	1.89%	1.89%	1.84%	1.34%	1.09%	0.84%

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 Moderate Allocation Fund (USD $)	Expense Example, By Year, Column [Text]	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
A	Class A Shares	680	902	1,141	1,827
B	Class B Shares assuming redemption at end of period	587	879	1,196	1,962
C	Class C Shares assuming redemption at end of period	287	579	996	2,159
I	Class I Shares	86	268	466	1,037
529A	Class 529A Shares	685	926	1,187	1,931
529B	Class 529B Shares assuming redemption at end of period	592	904	1,242	2,066
529C	Class 529C Shares assuming redemption at end of period	292	604	1,042	2,260
R1	Class R1 Shares	187	579	996	2,159
R2	Class R2 Shares	136	425	734	1,613
R3	Class R3 Shares	111	347	601	1,329
R4	Class R4 Shares	86	268	466	1,037

Expense Example, No Redemption MFS Moderate Allocation Fund (USD $)	Expense Example, No Redemption, By Year, Column [Text]	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
B	Class B Shares assuming no redemption at end of period	187	579	996	1,962
C	Class C Shares assuming no redemption at end of period	187	579	996	2,159
529B	Class 529B Shares assuming no redemption at end of period	192	604	1,042	2,066
529C	Class 529C Shares assuming no redemption at end of period	192	604	1,042	2,260

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 6% of the average value of its portfolio.

Principal Investment Strategies

The fund is designed to provide diversification among different asset classes by
investing its assets in other mutual funds advised by MFS (Massachusetts
Financial Services Company, the fund's investment adviser), referred to as
underlying funds. The underlying funds are selected following a two stage asset
allocation process. The first stage is a strategic asset allocation to determine
the percentage of the fund's assets to be invested in the general asset classes
of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an
allocation to underlying funds that have less traditional investment strategies
that MFS believes provide diversification benefits when added to a portfolio
consisting of stock and bond funds (referred to as Specialty Funds). The second
stage involves the actual selection of underlying funds to represent the asset
classes based on underlying fund classifications, historical risk, performance,
and other factors. Within the stock fund allocations, MFS seeks to diversify
globally (by including domestic and international underlying funds), in terms of
market capitalization (by including large, mid, and small capitalization
underlying funds), and by style (by including both growth and value underlying
funds). Within the bond fund allocation, MFS includes underlying funds with
varying degrees of interest rate and credit exposure.

As of September 28, 2012, the fund's target allocation among asset classes and
the underlying funds was:

Bond Funds:                             40%
MFS Emerging Markets Debt Fund           3%
MFS Global Bond Fund                     5%
MFS Government Securities Fund          10%
MFS High Income Fund                     5%
MFS Inflation-Adjusted Bond Fund         5%
MFS Research Bond Fund                  12%
Specialty Funds:                         6%
MFS Absolute Return Fund                 1%
MFS Commodity Strategy Fund              3%
MFS Global Real Estate Fund              2%
International Stock Funds:              13%
MFS International Growth Fund            3%
MFS International New Discovery Fund     1%
MFS International Value Fund             3%
MFS Research International Fund          6%
U.S. Stock Funds:                       41%
MFS Growth Fund                          8%
MFS Mid Cap Growth Fund                  7%
MFS Mid Cap Value Fund                   7%
MFS New Discovery Fund                 1.5%
MFS New Discovery Value Fund           1.5%
MFS Research Fund                        8%
MFS Value Fund                           8%

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 and underlying funds 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.

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, political, regulatory, geopolitical, or 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 and 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, political, regulatory, geopolitical
or 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.

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, or 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.

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.

Commodity Risk:  The value of commodities may be more volatile than the value of
equity securities or debt instruments and their value may be affected by changes
in overall market movements, commodity index volatility, changes in interest
rates, or factors affecting a particular industry or commodity. The price of a
commodity may be affected by demand/supply imbalances in the market for the
commodity.

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; property tax
rates, 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 six-month period ended June 30, 2012 was 5.90%. During
the period(s) shown in the bar chart, the highest quarterly return was 13.80%
(for the calendar quarter ended June 30, 2009) and the lowest quarterly return
was (15.13)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2011)

Average Annual Total Returns MFS Moderate Allocation Fund	Label		1 Year	5 Years	Since Inception	Inception Date
A	A Shares Returns Before Taxes		(5.48%)	1.96%	5.18%	Jun. 28, 2002
B	B Shares Returns Before Taxes		(4.33%)	2.09%	5.26%	Jun. 28, 2002
C	C Shares Returns Before Taxes		(1.42%)	2.45%	5.14%	Jun. 28, 2002
I	I Shares Returns Before Taxes		0.53%	3.48%	6.21%	Jun. 28, 2002
529A	529A Shares Returns Before Taxes		(5.55%)	1.83%	5.00%	Jun. 28, 2002
529B	529B Shares Returns Before Taxes		(4.41%)	1.96%	5.07%	Jun. 28, 2002
529C	529C Shares Returns Before Taxes		(1.50%)	2.30%	4.95%	Jun. 28, 2002
R1	R1 Shares Returns Before Taxes		(0.53%)	2.42%	5.04%	Jun. 28, 2002
R2	R2 Shares Returns Before Taxes		(0.04%)	2.92%	5.54%	Jun. 28, 2002
R3	R3 Shares Returns Before Taxes		0.30%	3.19%	5.85%	Jun. 28, 2002
R4	R4 Shares Returns Before Taxes		0.53%	3.45%	6.13%	Jun. 28, 2002
After Taxes on Distributions A	A Shares Returns After Taxes on Distributions		(6.22%)	1.03%	4.38%	Jun. 28, 2002
After Taxes on Distributions and Sales A	A Shares Returns After Taxes on Distributions and Sale of Fund Shares		(3.44%)	1.22%	4.11%	Jun. 28, 2002
Standard & Poor's 500 Stock Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index		2.11%	(0.25%)	4.59%	Jun. 28, 2002
MFS Moderate Allocation Fund Blended Index	Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Moderate Allocation Fund Blended Index	[1]	2.22%	2.30%	5.37%	Jun. 28, 2002

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

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

[1] MFS Fund Distributors, Inc., has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2013, unless MFS Fund Distributors, Inc., elects to extend the waiver.

[1] The MFS Moderate Allocation Fund Blended Index (the "Blended Index") is at a point in time and allocations during the period can change. At period end, the Blended Index was composed of the following amounts of the following indices: (41%) Standard & Poor's 500 Stock Index; (13%) MSCI EAFE (Europe, Australasia, Far East) Index; (3%) The Dow Jones-UBS Commodity Index; (2%) FTSE EPRA/NAREIT Developed Real Estate Index ; and (41%) Barclays U.S. Aggregate Bond Index.