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Performance Management
Aug. 31, 2025
MFS Core Equity Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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.comor by calling 1-800-225-2606.
Performance Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Footnotes [Text Block] *Included in the Class A total return for the 2017 calendar year are proceeds received from a non-recurring litigation settlement against Household International, Inc. Had these proceeds not been included, the calendar year 2017 total return would have been lower by 0.89%.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 10.94%. During the period(s) shown in the bar chart, the highest quarterly return was 20.41% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (19.04)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Core Equity Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Russell 3000® Index | Average Annual Return, Label [Optional Text] Russell 3000® Index      
Russell 3000® Index | Average Annual Return, Percent   23.81% 13.86% 12.55%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   13.17% 11.29% 11.59%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   11.12% 10.03% 10.05%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   9.23% 8.77% 9.04%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   15.18% 11.52% 11.58%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   18.20% 11.77% 11.58%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   20.41% 12.90% 12.53%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   19.20% 11.78% 11.41%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   19.79% 12.35% 11.98%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   20.08% 12.62% 12.24%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   20.36% 12.90% 12.53%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   20.49% 13.00% 12.63%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Core Equity Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 10.94%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 20.41%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (19.04%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Low Volatility Equity Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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 also reflects the fund’s principal investment strategies.

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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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 also reflects the fund’s principal investment strategies.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 9.67%. During the period(s) shown in the bar chart, the highest quarterly return was 14.57% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (18.26)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Low Volatility Equity Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Standard & Poor's 500 Stock Index | Average Annual Return, Label [Optional Text] Standard & Poor's 500 Stock Index      
Standard & Poor's 500 Stock Index | Average Annual Return, Percent   25.02% 14.53% 13.10%
MSCI USA Minimum Volatility Index (net div) | Average Annual Return, Label [Optional Text] MSCI USA Minimum Volatility Index (net div)      
MSCI USA Minimum Volatility Index (net div) | Average Annual Return, Percent   15.38% 7.56% 9.68%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   7.14% 8.33% 9.56%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   4.18% 6.52% 8.34%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   6.39% 6.40% 7.66%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   8.80% 8.50% 9.55%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   11.85% 8.81% 9.55%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   13.93% 9.89% 10.48%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   12.82% 8.79% 9.39%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   13.35% 9.34% 9.94%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   13.68% 9.62% 10.22%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   13.93% 9.89% 10.48%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   14.01% 9.99% 10.58%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Low Volatility Equity Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 9.67%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 14.57%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (18.26%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Low Volatility Global Equity Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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 also reflects the fund's principal investment strategies.

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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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 also reflects the fund's principal investment strategies.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 14.25%. During the period(s) shown in the bar chart, the highest quarterly return was 11.25% (for the calendar quarter ended

June 30, 2020) and the lowest quarterly return was (18.01)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Low Volatility Global Equity Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
MSCI All Country World Index (net div) | Average Annual Return, Label [Optional Text] MSCI All Country World Index (net div)      
MSCI All Country World Index (net div) | Average Annual Return, Percent   17.49% 10.06% 9.23%
MSCI All Country World Minimum Volatility Index (net div) | Average Annual Return, Label [Optional Text] MSCI All Country World Minimum Volatility Index (net div)      
MSCI All Country World Minimum Volatility Index (net div) | Average Annual Return, Percent   11.37% 4.72% 6.93%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   5.92% 6.17% 7.16%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   4.17% 5.13% 6.35%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   4.81% 4.80% 5.71%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   7.51% 6.33% 7.13%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   10.55% 6.64% 7.14%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   12.66% 7.70% 8.04%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   11.55% 6.64% 6.97%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   12.09% 7.18% 7.51%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   12.36% 7.45% 7.79%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   12.66% 7.70% 8.05%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   12.77% 7.80% 8.12%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Low Volatility Global Equity Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 14.25%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 11.25%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (18.01%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS New Discovery Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 7.95%. During the period(s) shown in the bar chart, the highest quarterly return was 34.61% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (22.25)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS New Discovery Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Russell 3000® Index | Average Annual Return, Label [Optional Text] Russell 3000® Index      
Russell 3000® Index | Average Annual Return, Percent   23.81% 13.86% 12.55%
Russell 2000® Growth Index | Average Annual Return, Label [Optional Text] Russell 2000® Growth Index      
Russell 2000® Growth Index | Average Annual Return, Percent   15.15% 6.86% 8.09%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   (0.05%) 3.21% 8.07%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   (0.05%) 1.27% 5.82%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   (0.03%) 2.22% 5.91%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   1.32% 3.41% 8.05%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   4.29% 3.66% 8.06%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   6.32% 4.71% 8.98%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   5.27% 3.67% 7.90%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   5.81% 4.18% 8.44%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   6.06% 4.44% 8.71%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   6.33% 4.70% 8.99%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   6.46% 4.83% 9.10%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS New Discovery Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 7.95%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 34.61%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (22.25%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Research International Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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) one or more other measures of performance for markets 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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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) one or more other measures of performance for markets in which the fund invests.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 17.77%. During the period(s) shown in the bar chart, the highest quarterly return was 16.46% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (19.70)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Research International Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
MSCI EAFE (Europe, Australasia, Far East) Index (net div) | Average Annual Return, Label [Optional Text] MSCI EAFE (Europe, Australasia, Far East) Index (net div)      
MSCI EAFE (Europe, Australasia, Far East) Index (net div) | Average Annual Return, Percent   3.82% 4.73% 5.20%
MSCI All Country World (ex-US) Index (net div) | Average Annual Return, Label [Optional Text] MSCI All Country World (ex-US) Index (net div)      
MSCI All Country World (ex-US) Index (net div) | Average Annual Return, Percent   5.53% 4.10% 4.80%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   (3.07%) 2.64% 4.47%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   (3.36%) 2.44% 4.16%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   (1.41%) 2.14% 3.60%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   (1.97%) 2.73% 4.46%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   1.05% 3.09% 4.46%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   3.07% 4.12% 5.35%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   2.07% 3.07% 4.29%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   2.55% 3.60% 4.82%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   2.83% 3.87% 5.08%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   3.06% 4.12% 5.34%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   3.19% 4.23% 5.45%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Research International Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 17.77%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 16.46%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (19.70%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Technology Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 12.70%. During the period(s) shown in the bar chart, the highest quarterly return was 30.74% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (21.77)% (for the calendar quarter ended June 30, 2022).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Technology Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Standard & Poor's 500 Stock Index | Average Annual Return, Label [Optional Text] Standard & Poor's 500 Stock Index      
Standard & Poor's 500 Stock Index | Average Annual Return, Percent   25.02% 14.53% 13.10%
Standard & Poor's North American Technology Sector Index | Average Annual Return, Label [Optional Text] Standard & Poor's North American Technology Sector Index      
Standard & Poor's North American Technology Sector Index | Average Annual Return, Percent   36.08% 21.06% 20.70%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   28.63% 15.89% 16.90%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   24.34% 13.00% 14.97%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   19.62% 12.14% 13.80%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   31.44% 16.18% 16.88%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   34.44% 16.40% 16.89%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   36.81% 17.57% 17.89%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   35.47% 16.40% 16.72%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   36.17% 16.99% 17.30%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   36.47% 17.27% 17.59%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   36.83% 17.57% 17.89%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   36.95% 17.68% 18.00%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Technology Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 12.70%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 30.74%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (21.77%)
Lowest Quarterly Return, Date Jun. 30, 2022
MFS U.S. Government Cash Reserve Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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.

The fund’s past performance 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 Past Does Not Indicate Future [Text] The fund’s past performance does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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.
Bar Chart [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 2.96%. During the period(s) shown in the bar chart, the highest quarterly return was 1.25% (for the calendar quarter ended December 31, 2023) and the lowest quarterly return was 0.00% (for the calendar quarter ended March 31, 2022).
Performance Table Heading Performance Table.
Performance [Table]
Average Annual Total Returns - MFS U.S. Government Cash Reserve Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Class A | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class B | Average Annual Return, Percent 0.87% 1.77% 1.35%
Class C | Average Annual Return, Percent 3.87% 2.14% 1.35%
Class I | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class R1 | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class R2 | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class R3 | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class R4 | Average Annual Return, Percent 4.87% 2.14% 1.35%
Class R6 | Average Annual Return, Percent 4.92% 2.18% 1.37%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS U.S. Government Cash Reserve Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 2.96%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 1.25%
Highest Quarterly Return, Date Dec. 31, 2023
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return none
Lowest Quarterly Return, Date Mar. 31, 2022
MFS Value Fund  
Prospectus [Line Items]  
Bar Chart and Performance Table [Heading] Performance Information
Performance Narrative [Text Block]

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 Past Does Not Indicate Future [Text] The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] 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.
Bar Chart Narrative [Text Block] 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] 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 [Heading] Class A Bar Chart.
Bar Chart Closing [Text Block]

The total return for the nine-month period ended September 30, 2025, was 10.57%. During the period(s) shown in the bar chart, the highest quarterly return was 14.23% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (23.82)% (for the calendar quarter ended March 31, 2020).
Performance Table Heading Performance Table.
Performance Table Not Relevant to Tax Deferred 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]
Average Annual Total Returns - MFS Value Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Aug. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Russell 3000® Index | Average Annual Return, Label [Optional Text] Russell 3000® Index      
Russell 3000® Index | Average Annual Return, Percent   23.81% 13.86% 12.55%
Russell 1000® Value Index | Average Annual Return, Label [Optional Text] Russell 1000® Value Index      
Russell 1000® Value Index | Average Annual Return, Percent   14.37% 8.68% 8.49%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   5.22% 6.68% 7.90%
Class A | After Taxes on Distributions | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions      
Class A | After Taxes on Distributions | Average Annual Return, Percent   3.15% 5.21% 6.66%
Class A | After Taxes on Distributions and Sales | Average Annual Return, Label [Optional Text] Returns After Taxes on Distributions and Sale of Fund Shares      
Class A | After Taxes on Distributions and Sales | Average Annual Return, Percent   4.62% 5.10% 6.17%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   6.79% 6.84% 7.89%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   9.80% 7.15% 7.89%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   11.90% 8.22% 8.81%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   10.81% 7.15% 7.73%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   11.35% 7.68% 8.27%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   11.64% 7.95% 8.54%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   11.90% 8.22% 8.81%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   12.02% 8.34% 8.92%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2024)
Performance Table One Class of after Tax Shown [Text] 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.
Index No Deduction for Fees, Expenses, or Taxes [Text] Reflects no deduction for fees, expenses, or taxes
Performance Table Closing [Text Block]

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.
Performance Availability Website Address [Text] mfs.com
Performance Availability Phone [Text] 1-800-225-2606
MFS Value Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the nine-month period ended
Bar Chart, Year to Date Return 10.57%
Bar Chart, Year to Date Return, Date Sep. 30, 2025
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 14.23%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (23.82%)
Lowest Quarterly Return, Date Mar. 31, 2020