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MFS® Blended Research® Small Cap Equity Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MFS® Blended Research® Small Cap Equity Fund Summary of Key Information
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

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


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 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 Sep. 30, 2017
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.  For the period from the fund’s commencement of operations on September 15, 2015 to the fund’s fiscal year end of May 31, 2016, the fund’s portfolio turnover rate was 47% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 47.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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


The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in equity securities of issuers with small market capitalizations. MFS generally defines small market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell 2000® Index (the “Index”) over the last 13 months at the time of purchase. As of August 31, 2016, the range of the market capitalizations of the issuers in the Index was between $10.7 million and $4.7 billion.


Equity securities include common stocks, equity interests in real estate investment trusts (REITs), and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.


In selecting investments for the fund, MFS is not constrained to any particular investment style. MFS may invest the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies.


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


MFS normally allocates the fund’s investments across different industries and sectors, but MFS may invest a significant percentage of the fund’s assets in issuers in a single or small number of industries or sectors.


MFS uses a bottom-up approach to buying and selling investments for the fund. Investments are selected primarily based on blending fundamental and quantitative research. MFS uses fundamental analysis of individual issuers to determine a fundamental rating for an issuer.  MFS uses quantitative analysis to determine a quantitative rating for an issuer. MFS then constructs the portfolio considering the blended rating from combining the fundamental rating and the quantitative rating, as well as issuer, industry, and sector weightings, market capitalization, volatility, and other factors, with a goal of constructing a portfolio with a target predicted tracking error of approximately 3% compared to the Index.  Tracking error generally measures how the differences between the fund’s monthly returns and the Index’s monthly returns have varied over a specified time period.


For purposes of the fund’s 80% policy, net assets include the amount of any borrowings for investment purposes.

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.


Investment Strategy Risk:  There is no assurance that the fund will meet its target predicted tracking error over the long term or for any year or period of years, or that the fund’s predicted tracking error and actual tracking error will be similar.  The fund’s strategy to target a predicted tracking error of approximately 3% compared to the Index and to blend fundamental and quantitative research may not produce the intended results. In addition, MFS fundamental research is not available for all issuers.


Small Cap Risk:  The stocks of small cap companies can be more volatile and their shares can be less liquid than those of larger companies.


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


Real Estate Investment Trust Risk: The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; difficulties in valuing and disposing of real estate; 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; the management skill and creditworthiness of the REIT manager; 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.


Industry and Sector Focus Risk:  Issuers in an industry or sector can react similarly to market, economic, political, regulatory, geopolitical, and other conditions.  If MFS invests a significant percentage of the fund’s assets in issuers within an industry or sector, the fund’s performance will be affected by conditions in that industry or sector.


Liquidity Risk:  It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at a price or time that is not advantageous in order to meet redemptions or other cash needs.


Investment Selection Risk:  MFS’ investment analysis, its development and use of quantitative models, 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. Investments selected using quantitative models may not produce the intended results due to the factors used in the models, the weight placed on each factor in the models, changing sources of market return, and technical issues in the design, development, implementation, and maintenance of the models (e.g., incomplete or inaccurate data, programming or other software issues, and technology failures).
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® Blended Research® Small Cap Equity Fund | A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 1.00% [1]
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.39%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.99%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 670
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,906
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,107
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,967
MFS® Blended Research® Small Cap Equity Fund | 529A  
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 none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 5.59%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.49%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.45%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 675
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,928
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,144
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 6,028
MFS® Blended Research® Small Cap Equity Fund | 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 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.14%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 577
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,917
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,191
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 6,085
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 177
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,620
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 3,002
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 6,085
MFS® Blended Research® Small Cap Equity Fund | 529B  
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 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 5.59%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.24%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.45%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.79%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 582
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,939
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,228
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 6,145
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 182
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,643
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 3,040
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 6,145
MFS® Blended Research® Small Cap Equity Fund | C  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.14%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 277
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,620
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,002
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 6,207
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 177
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,620
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 3,002
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 6,207
MFS® Blended Research® Small Cap Equity Fund | 529C  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 5.59%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.24%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.45%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.79%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 282
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,643
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,040
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 6,266
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 182
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,643
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 3,040
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 6,266
MFS® Blended Research® Small Cap Equity Fund | I  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.14%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 76
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,341
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,578
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,550
MFS® Blended Research® Small Cap Equity Fund | R1  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.14%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 177
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,620
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,002
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 6,207
MFS® Blended Research® Small Cap Equity Fund | R2  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.64%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
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 1,482
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,793
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,888
MFS® Blended Research® Small Cap Equity Fund | R3  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.39%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
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 1,412
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,686
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,721
MFS® Blended Research® Small Cap Equity Fund | R4  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 5.49%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.14%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.40%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 76
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,341
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,578
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,550
MFS® Blended Research® Small Cap Equity Fund | Class R6  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, whichever is less) rr_MaximumDeferredSalesChargeOverOther none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 5.48%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.13%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.43%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.70%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 72
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,336
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,572
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,541
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
[2] 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 class' average daily net assets attributable to each share class annually. This written agreement will expire on September 30, 2017, unless MFS Fund Distributors, Inc., elects to extend the waiver. Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.99% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.74% of the class' average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.74% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.24% of the class' average daily net assets annually for Class R2 shares, 0.70% of the class' average daily net assets annually for Class R6 shares, 1.04% of the class' average daily net assets annually for Class 529A shares, and 1.79% of the class' average daily net asset annually for each of Class 529B and Class 529C 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, 2017.