v3.26.3
Label Element Value
MFS International Growth Fund  
Risk/Return: oef_RiskReturnAbstract  
Risk/Return [Heading] oef_RiskReturnHeading MFS® International Growth Fund Summary of Key Information
Objective [Heading] oef_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] oef_ObjectivePrimaryTextBlock

The fund’s investment objective is to seek capital appreciation.

Expense Heading [Optional Text] oef_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] oef_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell 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 [Optional Text] oef_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Optional Text] oef_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Portfolio Turnover [Heading] oef_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] oef_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 16% of the average value of its portfolio.
Portfolio Turnover, Rate oef_PortfolioTurnoverRate 16.00%
Expense Breakpoint Discounts [Text] oef_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] oef_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] oef_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] oef_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] oef_ExpenseExampleByYearCaption Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Strategy [Heading] oef_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] oef_StrategyNarrativeTextBlock

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in growth companies. MFS defines growth companies as companies that MFS believes have above average earnings growth potential compared to other companies. MFS considers a number of factors when determining a company’s growth potential, including whether (i) the issuer is included in an index that is representative of growth companies; (ii) the issuer is classified as a growth company by an independent third party financial data provider; and/or (iii) the issuer exhibits the characteristics of a growth company, considering metrics such as historical and/or projected earnings, sales, or free cash flow growth rates compared to the applicable equity market and/or to issuers in the same sector or industry. In assessing the growth potential of an issuer, MFS may also consider measures of financial quality, such as indicators of profitability (i.e., return on equity and return on invested capital), balance sheet strength (including leverage and interest coverage ratios), an issuer’s research and development expenses relative to sales, and whether an issuer is raising capital to grow, fund, or expand its business. Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures.

MFS normally invests the fund’s assets primarily in foreign equity securities, including emerging market equity securities. Emerging market countries are countries with financial and capital markets in the development phase. Emerging market countries include countries located in Latin America, Asia, Africa, the Middle East, and developing countries of Europe, primarily Eastern Europe. Equity securities include common stocks, depositary receipts, and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.

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

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

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative screening tools that systematically evaluate issuers may also be considered.

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

Summary of Definition of Rule 35d-1 Term in Fund Name [Text Block] fnd_NmRule35d1TermDfnSmryTextBlock MFS defines growth companies as companies that MFS believes have above average earnings growth potential compared to other companies. MFS considers a number of factors when determining a company’s growth potential, including whether (i) the issuer is included in an index that is representative of growth companies; (ii) the issuer is classified as a growth company by an independent third party financial data provider; and/or (iii) the issuer exhibits the characteristics of a growth company, considering metrics such as historical and/or projected earnings, sales, or free cash flow growth rates compared to the applicable equity market and/or to issuers in the same sector or industry. In assessing the growth potential of an issuer, MFS may also consider measures of financial quality, such as indicators of profitability (i.e., return on equity and return on invested capital), balance sheet strength (including leverage and interest coverage ratios), an issuer’s research and development expenses relative to sales, and whether an issuer is raising capital to grow, fund, or expand its business. Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures.
Summary of Selection Criteria for Rule 35d-1 Term in Fund Name [Text Block] fnd_NmRule35d1TermSlctnCritSmryTextBlock MFS defines growth companies as companies that MFS believes have above average earnings growth potential compared to other companies. MFS considers a number of factors when determining a company’s growth potential, including whether (i) the issuer is included in an index that is representative of growth companies; (ii) the issuer is classified as a growth company by an independent third party financial data provider; and/or (iii) the issuer exhibits the characteristics of a growth company, considering metrics such as historical and/or projected earnings, sales, or free cash flow growth rates compared to the applicable equity market and/or to issuers in the same sector or industry. In assessing the growth potential of an issuer, MFS may also consider measures of financial quality, such as indicators of profitability (i.e., return on equity and return on invested capital), balance sheet strength (including leverage and interest coverage ratios), an issuer’s research and development expenses relative to sales, and whether an issuer is raising capital to grow, fund, or expand its business. Growth companies tend to have stock prices that are high relative to their earnings, dividends, book value, or other financial measures.
Rule 35d-1 Eighty Percent Investment Policy [Text Block] fnd_NmRule35d1EightyPctInvstmntPlcyTextBlock MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in growth companies.
Bar Chart and Performance Table [Heading] oef_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] oef_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 (i) a broad measure of market performance and (ii) the performance of an additional index that the adviser believes more closely reflects the market segments in which the fund invests.

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] oef_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 (i) a broad measure of market performance and (ii) the performance of an additional index that the adviser believes more closely reflects the market segments in which the fund invests.
Performance Availability Phone [Text] oef_PerformanceAvailabilityPhone 1-800-225-2606
Performance Availability Website Address [Text] oef_PerformanceAvailabilityWebSiteAddress mfs.com
Performance Past Does Not Indicate Future [Text] oef_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] oef_BarChartHeading Class A Bar Chart.
Bar Chart Narrative [Text Block] oef_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] oef_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] oef_BarChartClosingTextBlock

The total return for the six-month period ended June 30, 2026, was 1.82%. During the period(s) shown in the bar chart, the highest quarterly return was 16.93% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (18.71)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading oef_PerformanceTableHeading Performance Table.
Index No Deduction for Fees, Expenses, or Taxes [Text] oef_IndexNoDeductionForFeesExpensesTaxes Reflects no deduction for fees, expenses, or taxes
Performance Table Not Relevant to Tax Deferred oef_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 (IRAs).
Performance Table One Class of after Tax Shown [Text] oef_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] oef_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual U.S. 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 (IRAs). 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 [Optional Text] oef_AverageAnnualReturnCaption Average Annual Total Returns (For the Periods Ended December 31, 2025)
MFS International Growth Fund | Principal Risks  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

Principal Risks

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

The principal risks of investing in the fund are:
MFS International Growth Fund | Risk Lose Money [Member]  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
MFS International Growth Fund | Risk Not Insured [Member]  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock 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.
MFS International Growth Fund | Investment Selection Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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. In addition, to the extent MFS considers quantitative tools in managing the fund, such tools may not produce the intended results.

MFS International Growth Fund | Equity Market Risk/Company Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

Equity Market Risk/Company Risk: Equity markets are volatile and can decline significantly in response to changes in, 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. The value of an investment held by the fund may decline due to factors directly related to the issuer.
MFS International Growth Fund | Growth Company Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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.
MFS International Growth Fund | Foreign Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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 markets or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S.

investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

MFS International Growth Fund | Emerging Markets Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

Emerging Markets Risk: Investments tied economically to emerging markets, especially frontier markets, can involve additional and greater risks than the risks associated with investments in developed markets. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, greater government involvement in the economy, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater political, social, geopolitical, and economic instability than developed markets.

MFS International Growth Fund | Currency Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

Currency Risk: The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, and changes in currency exchange rates impact the financial condition of companies or other issuers and may change the value in U.S. dollars of investments denominated in foreign currencies.

MFS International Growth Fund | Focus Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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. Furthermore, investments in particular industries, sectors, countries, or regions may be more volatile than the broader market as a whole.

MFS International Growth Fund | Liquidity Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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.

MFS International Growth Fund | Large Shareholder Risk  
Risk/Return: oef_RiskReturnAbstract  
Risk [Text Block] oef_RiskTextBlock

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 and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would.
MFS International Growth Fund | MSCI All Country World (ex-US) Index (net div)  
Risk/Return: oef_RiskReturnAbstract  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel MSCI All Country World (ex-US) Index (net div)
Average Annual Return, Percent oef_AvgAnnlRtrPct 32.39%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.91%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.41%
MFS International Growth Fund | MSCI All Country World (ex-US) Growth Index (net div)  
Risk/Return: oef_RiskReturnAbstract  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel MSCI All Country World (ex-US) Growth Index (net div)
Average Annual Return, Percent oef_AvgAnnlRtrPct 25.65%
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.01%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.92%
MFS International Growth Fund | Class A  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.05%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.04%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expenses Deferred Charges [Text Block] oef_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 oef_ExpenseExampleYear01 $ 675
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 889
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 1,120
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 1,783
Year to Date Return, Label [Optional Text] oef_YearToDateReturnLabel The total return for the six-month period ended
Bar Chart, Year to Date Return, Date oef_BarChartYearToDateReturnDate Jun. 30, 2026
Bar Chart, Year to Date Return oef_BarChartYearToDateReturn 1.82%
Highest Quarterly Return, Label [Optional Text] oef_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date oef_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return oef_BarChartHighestQuarterlyReturn 16.93%
Lowest Quarterly Return, Label [Optional Text] oef_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date oef_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return oef_BarChartLowestQuarterlyReturn (18.71%)
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.84%
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.59%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.99%
Annual Return [Percent] oef_AnnlRtrPct 2.39%
Annual Return [Percent] oef_AnnlRtrPct 32.17%
Annual Return [Percent] oef_AnnlRtrPct (9.08%)
Annual Return [Percent] oef_AnnlRtrPct 26.82%
Annual Return [Percent] oef_AnnlRtrPct 15.45%
Annual Return [Percent] oef_AnnlRtrPct 9.23%
Annual Return [Percent] oef_AnnlRtrPct (15.32%)
Annual Return [Percent] oef_AnnlRtrPct 14.52%
Annual Return [Percent] oef_AnnlRtrPct 8.84%
Annual Return [Percent] oef_AnnlRtrPct 20.78%
MFS International Growth Fund | Class A | After Taxes on Distributions  
Risk/Return: oef_RiskReturnAbstract  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns After Taxes on Distributions
Average Annual Return, Percent oef_AvgAnnlRtrPct 12.56%
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.59%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.29%
MFS International Growth Fund | Class A | After Taxes on Distributions and Sales  
Risk/Return: oef_RiskReturnAbstract  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent oef_AvgAnnlRtrPct 9.28%
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.32%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.32%
MFS International Growth Fund | Class B  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRBX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 4.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.80%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.79%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 582 [3]
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 865 [3]
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 1,174 [3]
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 1,918 [3]
Expense Example, No Redemption, 1 Year oef_ExpenseExampleNoRedemptionYear01 182 [3]
Expense Example, No Redemption, 3 Years oef_ExpenseExampleNoRedemptionYear03 565 [3]
Expense Example, No Redemption, 5 Years oef_ExpenseExampleNoRedemptionYear05 974 [3]
Expense Example, No Redemption, 10 Years oef_ExpenseExampleNoRedemptionYear10 $ 1,918 [3]
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 15.87%
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.73%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.97%
MFS International Growth Fund | Class C  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.80%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.79%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 282 [3]
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 565 [3]
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 974 [3]
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 1,918 [3]
Expense Example, No Redemption, 1 Year oef_ExpenseExampleNoRedemptionYear01 182 [3]
Expense Example, No Redemption, 3 Years oef_ExpenseExampleNoRedemptionYear03 565 [3]
Expense Example, No Redemption, 5 Years oef_ExpenseExampleNoRedemptionYear05 974 [3]
Expense Example, No Redemption, 10 Years oef_ExpenseExampleNoRedemptionYear10 $ 1,918 [3]
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 18.89%
Average Annual Return, Percent oef_AvgAnnlRtrPct 6.05%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.98%
MFS International Growth Fund | Class I  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MQGIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.80%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 0.79%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 81
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 254
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 443
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 989
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 21.08%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.11%
Average Annual Return, Percent oef_AvgAnnlRtrPct 9.90%
MFS International Growth Fund | Class R1  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.80%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.79%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 182
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 565
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 974
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 2,115
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 19.88%
Average Annual Return, Percent oef_AvgAnnlRtrPct 6.05%
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.81%
MFS International Growth Fund | Class R2  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.30%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.29%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 131
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 411
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 712
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 1,567
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 20.48%
Average Annual Return, Percent oef_AvgAnnlRtrPct 6.58%
Average Annual Return, Percent oef_AvgAnnlRtrPct 9.36%
MFS International Growth Fund | Class R3  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRTX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 1.05%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 1.04%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 106
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 333
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 578
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 1,282
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 20.78%
Average Annual Return, Percent oef_AvgAnnlRtrPct 6.84%
Average Annual Return, Percent oef_AvgAnnlRtrPct 9.63%
MFS International Growth Fund | Class R4  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.80%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 0.79%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 81
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 254
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 443
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 989
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 21.09%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.12%
Average Annual Return, Percent oef_AvgAnnlRtrPct 9.91%
MFS International Growth Fund | Class R6  
Risk/Return: oef_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol MGRDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) oef_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.66%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.69%
Fee Waiver or Reimbursement oef_FeeWaiverOrReimbursementOverAssets (0.01%) [2]
Net Expenses (as a percentage of Assets) oef_NetExpensesOverAssets 0.68%
Fee Waiver or Reimbursement over Assets, Date of Termination oef_FeeWaiverOrReimbursementOverAssetsDateOfTermination September 30, 2027
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 69
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 220
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 383
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 858
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Returns Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 21.23%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.24%
Average Annual Return, Percent oef_AvgAnnlRtrPct 10.03%
[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 (MFS) has agreed in writing to waive at least 0.01% of the fund's management fee as part of an agreement pursuant to which MFS has agreed to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2027.
[3] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.