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MFS Blended Research Value Equity Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MFS Blended Research Value 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. Investors may also pay commissions or other fees to their financial intermediaries when they buy and hold shares of the fund, which are not reflected below.

 

You may qualify for sales charge reductions if, with respect to Class A shares, 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 and Reductions” on page 10 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

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, 2021
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 45% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 45.00%
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 actively identifying potential investments based on fundamental and quantitative analysis and then constructing a portfolio from these potential investments while managing various risk factors (e.g., issuer, industry, and sector weightings, market capitalization, and volatility) compared to the Russell 1000® Value Index, which represents the fund’s investment universe.

 

MFS normally invests at least 80% of the fund’s net assets in equity securities.

 

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.

 

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

 

While MFS may invest the fund’s assets in securities of companies of any size, MFS primarily invests in securities of companies with large capitalizations.

 

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

 

MFS normally invests the fund’s assets across different industries and sectors, but MFS may invest a significant percentage of the fund’s assets in issuers in a single industry or sector.

 

MFS uses an active 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 combines the fundamental rating with the quantitative rating to create a blended rating for an issuer. When an MFS fundamental rating is not available, MFS treats the issuer as having a neutral fundamental rating.

 

MFS constructs the portfolio using a portfolio optimization process that considers the blended rating, as well as issuer, industry, and sector weightings, market capitalization, volatility, and other factors.  The portfolio managers have the discretion to adjust the inputs and parameters used in the optimization process and the fund’s portfolio holdings based on factors such as the desired portfolio characteristics and the portfolio managers’ qualitative assessment of the optimization results.  MFS’ goal is to construct an actively managed portfolio with a target predicted tracking error of approximately 2% compared to the Russell 1000® Value Index.  Tracking error generally measures how the differences between the fund’s returns and the Russell 1000® Value Index’s returns have varied over a period of time.

 

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:

 

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. The quantitative models used by MFS (both proprietary and third-party) may not produce the intended results for a variety of reasons, including the factors used in the models, the weight placed on each factor in the models, changes from the market factors’ historical trends, changing sources of market return or market risk, and technical issues in the design, development, implementation, application, and maintenance of the models (e.g., incomplete, stale, or inaccurate data, programming or other software issues, coding errors, and technology failures).

 

Equity Market Risk/Company Risk:  Equity markets are volatile and can decline significantly in response to, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions.  These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general.  Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market.

 

Investment Strategy Risk:  There is no assurance that the fund’s predicted tracking error will equal its target predicted tracking error at any point in time or consistently for any period of time, 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 2% compared to the Russell 1000® Value 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.

 

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 Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging and frontier 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.

 

REITs 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.

 

Focus Risk:  Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund’s performance will be affected by the conditions in the industries, sectors, countries and regions to which the fund is exposed.

 

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 prices or times that are not advantageous in order to meet redemptions or other cash needs.

 

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares.  These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices.  Redemptions of a large number of shares also may increase transaction costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities.

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 [Text] rr_RiskNotInsured 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, 2020, was (16.83)%. During the period(s) shown in the bar chart, the highest quarterly return was 11.39% (for the calendar quarter ended March 31, 2019) and the lowest quarterly return was (12.23)% (for the calendar quarter ended December 31, 2018).

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, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn (16.83%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.39%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (12.23%)
Performance Table Heading rr_PerformanceTableHeading Performance Table.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (Reflects no deduction for fees, expenses, or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table 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-advantaged 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.
Average Annual Return, Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (For the Periods Ended December 31, 2019)
MFS Blended Research Value Equity Fund | Russell 1000® Value Index  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 26.54%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 11.80%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.74%
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 Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if, with respect to Class A shares, 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, with Redemption, 1 Year rr_ExpenseExampleYear01 646
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 832
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,034
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,615
Annual Return 2016 rr_AnnualReturn2016 13.85%
Annual Return 2017 rr_AnnualReturn2017 16.36%
Annual Return 2018 rr_AnnualReturn2018 (8.58%)
Annual Return 2019 rr_AnnualReturn2019 23.00%
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 15.92%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.93%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value Equity Fund | A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 15.40%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.13%
MFS Blended Research Value Equity Fund | A | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 9.80%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 6.81%
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice 4.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.66%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 552
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 807
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,086
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,751
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 152
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 507
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 886
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,751
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 18.10%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.30%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.66%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 252
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 507
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 886
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,951
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 152
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 507
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 886
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,951
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 21.08%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.63%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.66%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 194
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 351
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 806
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 23.33%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.73%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.66%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 1.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 152
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 507
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 886
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,951
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 22.15%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.64%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.16%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 352
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 622
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,394
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 22.76%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.20%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.91%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 76
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 273
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 487
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,104
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 22.99%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.48%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.26%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.66%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.17%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 194
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 351
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 806
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 23.38%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.75%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
MFS Blended Research Value Equity Fund | 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fee rr_ManagementFeesOverAssets 0.40%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.16%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.56%
Fee Reductions and/or Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.11%) [2]
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 168
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 302
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 691
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 23.38%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.82%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 15, 2015
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
[2] Massachusetts Financial Services Company has agreed in writing to bear the fund’s expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund’s investment activity), such that “Total Annual Fund Operating Expenses” do not exceed 0.74% of the class’ average daily net assets annually for each of Class A and Class R3 shares, 1.49% of the class’ average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.49% of the class’ average daily net assets annually for each of Class I and Class R4 shares, 0.99% of the class’ average daily net assets annually for Class R2 shares, and 0.45% of the class’ average daily net assets annually for Class R6 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, 2021.