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Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MFS® Global Multi-Asset Fund Summary of Key Information
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

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

Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

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


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 12 of the fund’s prospectus and “Waivers of Sales Charges” on page H-1 of the fund’s Statement of Additional Information (“SAI”).

Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 2014-10-31
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 48% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 48.00%
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) seeks to achieve the fund’s objective by generating returns from (1) a strategic allocation to a mix of asset classes, (2) individual security selection of U.S. and foreign issuers within those asset classes, and (3) a tactical asset allocation overlay to manage the fund’s exposure to asset classes, markets, and currencies primarily using derivative instruments. 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.


Strategic Asset Class Allocation:  MFS determines the percentages of the fund’s assets to be invested in the general asset classes of bonds and stocks, as well as in other less-traditional asset classes that MFS believes provide diversification benefits when added to a portfolio consisting of bonds and stocks, such as commodity-related investments and real estate-related investments.  As of October 1, 2013, the fund’s target strategic exposures among asset classes were as follows: 15% in inflation-adjusted debt instruments; 35% in other debt instruments; 30% in equity securities; 15% in commodity-related investments; and 5% in real estate-related investments.


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.  Equity securities include common stocks, preferred stocks, securities convertible into stocks, equity interests in real estate investment trusts (REITs), and depositary receipts for such securities.


MFS may invest the fund’s assets in other mutual funds advised by MFS that invest in such asset classes instead of investing directly in such assets.


The strategic asset class allocations are not designed to take advantage of short-term market opportunities and have been selected for investment over longer time periods.  The strategic asset class allocations may be changed without shareholder approval or notice.  The actual strategic asset class weightings can deviate due to market movements and cash flows.  MFS periodically rebalances the fund’s strategic asset class weightings.  These target asset class weightings do not reflect the fund’s cash balance; some portion of the fund’s portfolio will be held in cash due to collateral requirements associated with the fund’s derivative transactions, purchase and redemption activity, and other short term cash needs.


Individual Security Selection:


In selecting direct investments for the fund, MFS may invest the fund’s assets in U.S. and foreign securities, including emerging market securities.


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


MFS generally seeks to diversify the fund’s equity investments in terms of market capitalization (e.g., small, mid, large cap), style (e.g., growth, value), and location (e.g., U.S., foreign).  These allocations may vary significantly from time to time.


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.


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.


A team of investment professionals selects investments for the fund. MFS allocates the fund’s assets to investment professionals by investment strategy. 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 and instruments. Quantitative models that systematically evaluate issuers and 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.


In managing the tactical overlay, MFS uses proprietary quantitative models and 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. After taking into account the tactical overlay, the fund’s exposure to the various asset classes, markets, and/or currencies may vary significantly from time to time. 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., the high yield bond market).


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.  After taking into account the tactical overlay, the fund’s net exposures to the asset classes referenced below, which may include exposure to U.S. and foreign issuers, will normally fall within the following ranges:


Asset Class

 

Range

Inflation-adjusted debt instruments

 

-5% to 35%

Debt instruments, excluding inflation-adjusted debt instruments

 

0% to 70%

Equity securities

 

0% to 60%

Commodity-related investments

 

-5% to 35%

Real estate-related investments

 

-10% to 20%


MFS’ tactical asset allocation process for the fund will typically make extensive use of derivatives.


MFS may also use derivatives to seek to limit the fund’s exposure to certain extreme market events.

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 development and use of quantitative models,  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 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 other entity responsible for payment, 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 other entity, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.


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


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.


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 and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; and other factors.  The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.


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


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


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


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.


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.


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 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 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 Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex As of December 31, 2012, the MFS Global Multi-Asset Blended Index (the "Blended Index") consisted of the following indices and weightings: 35% The Barclays Global Aggregate Bond Index; 15% Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index; 15% The Dow Jones-UBS Commodity Index; 5% FTSE EPRA/NAREIT Developed Real Estate Index; and 30% MSCI All Country World Index. The components and weightings of the Blended Index may have differed during the period, and may differ in the future.
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 nine-month period ended September 30, 2013 was (0.20)%. During the period(s) shown in the bar chart, the highest quarterly return was 5.55% (for the calendar quarter ended September 30, 2012) and the lowest quarterly return was (4.66)% (for the calendar quarter ended June 30, 2012).

Year to Date Return, Label rr_YearToDateReturnLabel total return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2013
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn (0.20%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.55%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2012
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.66%)
Performance Table Heading rr_PerformanceTableHeading Performance Table.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (Reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

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

Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (for the Periods Ended December 31, 2012)
MSCI All Country World Index (gross div)
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Index Comparison (Reflects no deduction for fees, expenses or taxes) MSCI All Country World Index (gross div)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 16.80%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 2.91%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
MFS Global Multi-Asset Blended Index
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Index Comparison (Reflects no deduction for fees, expenses or taxes) MFS Global Multi-Asset Blended Index
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 8.88% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.52% [1]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011 [1]
A
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 1.00% [2]
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.23%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.44%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock On shares purchased without an initial sales charge and redeemed within 18 months of purchase for shares purchased on or after August 1, 2012, and within 24 months of purchase for shares purchased prior to August 1, 2012.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 713
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,161
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,633
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,934
Annual Return 2012 rr_AnnualReturn2012 8.76%
Label rr_AverageAnnualReturnLabel A Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 2.51%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (3.01%)
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
A | After Taxes on Distributions
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns After Taxes on Distributions
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 2.51%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (3.32%)
A | After Taxes on Distributions and Sale of Fund Shares
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.63%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (2.69%)
B
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 4.00%
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.98%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 2.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 622
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,147
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,698
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,066
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 222
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 847
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,498
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 3,066
Label rr_AverageAnnualReturnLabel B Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 4.03%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (2.65%)
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
C
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.98%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 2.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 322
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 847
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,498
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,243
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 222
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 847
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,498
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 3,243
Label rr_AverageAnnualReturnLabel C Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 6.94%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (0.45%)
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
I
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.98%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 121
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 545
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 994
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,243
Label rr_AverageAnnualReturnLabel I Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 9.03%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.59%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
R1
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.98%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 2.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 222
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 847
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,498
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,243
Label rr_AverageAnnualReturnLabel R1 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 7.88%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (0.44%)
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
R2
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.48%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.69%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 172
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 697
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,249
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,756
Label rr_AverageAnnualReturnLabel R2 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 8.45%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.07%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
R3
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.23%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.44%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 147
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 621
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,123
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,503
Label rr_AverageAnnualReturnLabel R3 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 8.74%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.33%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
R4
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 1.09%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.98%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.79%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 121
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 545
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 994
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,243
Label rr_AverageAnnualReturnLabel R4 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 8.92%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.53%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
R5
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.72%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 1.07%
Acquired (Underlying) Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.17%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.96%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.78%) [3]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.18%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 120
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 540
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 985
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,222
Label rr_AverageAnnualReturnLabel R5 Shares Returns Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 9.03%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.59%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 30, 2011
[1] As of December 31, 2012, the MFS Global Multi-Asset Blended Index (the "Blended Index") consisted of the following indices and weightings: 35% The Barclays Global Aggregate Bond Index; 15% Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index; 15% The Dow Jones-UBS Commodity Index; 5% FTSE EPRA/NAREIT Developed Real Estate Index; and 30% MSCI All Country World Index. The components and weightings of the Blended Index may have differed during the period, and may differ in the future.
[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 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, and fees and expenses associated with investments in investment companies and other similar investment vehicles), such that "Total Annual Fund Operating Expenses" do not exceed 1.27% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 2.02% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 1.02% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.52% of the fund's average daily net assets annually for Class R2 shares, and 1.01% 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 October 31, 2014.