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MFS® International Growth Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MFS® International Growth 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):
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 20% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 20.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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


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

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in foreign equity securities, including emerging market equity securities. Equity securities include common stocks 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 to have above average earnings growth potential compared to other companies (growth companies).


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


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


MFS 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 investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative models that systematically evaluate issuers may also be considered.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.


The principal risks of investing in the fund are:


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


Foreign 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.


Emerging Markets Risk:  Investments in emerging markets can involve additional and greater risks than the risks associated with investments in developed foreign markets.  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.


Growth Company Risk:  The stocks of growth companies can be more sensitive to the company’s earnings and more volatile than the market in general.


Geographic Focus Risk: Issuers in a single country, a small number of countries, or a particular geographic region can react similarly to market, currency, political, economic, regulatory, geopolitical, and other conditions, and the fund’s performance will be affected by the conditions in the countries or regions in which the fund’s assets are invested.


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 and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.
Risk Lose Money [Text] rr_RiskLoseMoney As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

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


The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-225-2606
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress mfs.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Class A Bar Chart.
Bar Chart Narrative [Text Block] rr_BarChartNarrativeTextBlock

The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2016, was 2.02%. During the period(s) shown in the bar chart, the highest quarterly return was 23.27% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (19.64)% (for the calendar quarter ended September 30, 2011).

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, 2016
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 2.02%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 23.27%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.64%)
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-advantaged 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-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.

Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (For the Periods Ended December 31, 2015)
MFS® International Growth Fund | MSCI All Country World (ex-US) Growth Index  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Index Comparison (Reflects no deduction for fees, expenses, or taxes) MSCI All Country World (ex-US) Growth Index
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (0.91%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.48%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.02%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.22%
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 $ 692
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 940
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,207
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,967
Annual Return 2006 rr_AnnualReturn2006 25.72%
Annual Return 2007 rr_AnnualReturn2007 15.90%
Annual Return 2008 rr_AnnualReturn2008 (40.10%)
Annual Return 2009 rr_AnnualReturn2009 37.65%
Annual Return 2010 rr_AnnualReturn2010 14.99%
Annual Return 2011 rr_AnnualReturn2011 (10.85%)
Annual Return 2012 rr_AnnualReturn2012 19.39%
Annual Return 2013 rr_AnnualReturn2013 13.56%
Annual Return 2014 rr_AnnualReturn2014 (5.32%)
Annual Return 2015 rr_AnnualReturn2015 0.02%
Label rr_AverageAnnualReturnLabel A Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (5.73%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.53%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.07%
MFS® International Growth Fund | A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel A Shares Returns After Taxes on Distributions
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (5.83%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.37%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 3.57%
MFS® International Growth Fund | 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 Years rr_AverageAnnualReturnYear01 (2.91%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.31%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 3.34%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 600
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 918
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,262
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,102
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 200
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 618
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,062
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,102
Label rr_AverageAnnualReturnLabel B Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (4.65%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.61%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.09%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 300
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 618
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,062
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,296
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 200
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 618
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,062
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,296
Label rr_AverageAnnualReturnLabel C Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (1.69%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.97%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 3.94%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 99
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 309
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 536
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,190
Label rr_AverageAnnualReturnLabel I Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 0.30%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 3.00%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.98%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 200
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 618
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,062
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,296
Label rr_AverageAnnualReturnLabel R1 Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (0.70%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.97%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 3.94%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 465
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,757
Label rr_AverageAnnualReturnLabel R2 Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 (0.25%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.48%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.46%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.22%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 124
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 387
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 670
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,477
Label rr_AverageAnnualReturnLabel R3 Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 0.04%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.75%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.72%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.19%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 99
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 309
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 536
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,190
Label rr_AverageAnnualReturnLabel R4 Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 0.27%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 3.00%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.98%
MFS® International Growth 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 0.78%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.06%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.84%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 86
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 268
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 466
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,037
Label rr_AverageAnnualReturnLabel R6 Shares Returns Before Taxes
Average Annual Returns, 1 Years rr_AverageAnnualReturnYear01 0.40%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 3.05%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 4.96%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.