v3.26.1
Performance Management
Apr. 30, 2026
MFS Core Bond 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 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 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 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 Closing [Text Block]

The total return for the six-month period ended June 30, 2026, was 0.69%. During the period(s) shown in the bar chart, the highest quarterly return was 6.69% (for the calendar quarter ended December 31, 2023) and the lowest quarterly return was (3.02)% (for the calendar quarter ended September 30, 2023).
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 Bond Fund
 12 Months Ended 42 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Bloomberg U.S. Aggregate Bond Index | Average Annual Return, Label [Optional Text] Bloomberg U.S. Aggregate Bond Index    
Bloomberg U.S. Aggregate Bond Index | Average Annual Return, Percent   7.30% 3.54%
Bloomberg U.S. Aggregate Bond Index | Performance Inception Date     Jun. 22, 2022
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class A | Average Annual Return, Percent   2.29% 2.21%
Class A | Performance Inception Date     Jun. 22, 2022
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   0.42% 0.43%
Class A | After Taxes on Distributions | Performance Inception Date     Jun. 22, 2022
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   1.33% 0.90%
Class A | After Taxes on Distributions and Sales | Performance Inception Date     Jun. 22, 2022
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class C | Average Annual Return, Percent   5.04% 2.70%
Class C | Performance Inception Date     Jun. 22, 2022
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class I | Average Annual Return, Percent   7.08% 3.75%
Class I | Performance Inception Date     Jun. 22, 2022
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R1 | Average Annual Return, Percent   6.03% 2.70%
Class R1 | Performance Inception Date     Jun. 22, 2022
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R2 | Average Annual Return, Percent   6.67% 3.24%
Class R2 | Performance Inception Date     Jun. 22, 2022
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R3 | Average Annual Return, Percent   6.93% 3.49%
Class R3 | Performance Inception Date     Jun. 22, 2022
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R4 | Average Annual Return, Percent   7.20% 3.75%
Class R4 | Performance Inception Date     Jun. 22, 2022
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R6 | Average Annual Return, Percent   7.23% 3.78%
Class R6 | Performance Inception Date     Jun. 22, 2022
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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 Bond Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 0.69%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 6.69%
Highest Quarterly Return, Date Dec. 31, 2023
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (3.02%)
Lowest Quarterly Return, Date Sep. 30, 2023
MFS Lifetime Income 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime Income Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 71% Bloomberg U.S. Aggregate Bond Index; 20% Standard & Poor's 500 Stock Index; 5% MSCI EAFE Index (net div); 2% Bloomberg Commodity Index; and 2% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future.
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 six-month period ended June 30, 2026, was 3.93%. During the period(s) shown in the bar chart, the highest quarterly return was 8.99% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (7.41)% (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 Lifetime Income Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Bloomberg U.S. Aggregate Bond Index | Average Annual Return, Label [Optional Text] Bloomberg U.S. Aggregate Bond Index      
Bloomberg U.S. Aggregate Bond Index | Average Annual Return, Percent   7.30% (0.36%) 2.01%
MFS Lifetime Income Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime Income Fund Blended Index      
MFS Lifetime Income Fund Blended Index | Average Annual Return, Percent   10.80% 3.35% 5.07%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   4.31% 2.54% 4.56%
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   2.33% 0.79% 3.05%
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   2.94% 1.36% 3.03%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   4.13% 2.33% 4.38%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   7.13% 2.66% 4.39%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   9.29% 3.71% 5.28%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   8.12% 2.66% 4.23%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   8.67% 3.18% 4.75%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   8.94% 3.43% 5.01%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   9.30% 3.69% 5.27%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   9.31% 3.80% 5.39%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime Income Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 71% Bloomberg U.S. Aggregate Bond Index; 20% Standard & Poor's 500 Stock Index; 5% MSCI EAFE Index (net div); 2% Bloomberg Commodity Index; and 2% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future.

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 Lifetime Income Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 3.93%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 8.99%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (7.41%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2030 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2030 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 60.37% Bloomberg U.S. Aggregate Bond Index; 27.73% Standard & Poor's 500 Stock Index; 7.90% MSCI EAFE Index (net div); 2% Bloomberg Commodity Index; and 2% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 4.87%. During the period(s) shown in the bar chart, the highest quarterly return was 13.69% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (14.85)% (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 Lifetime 2030 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2030 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2030 Fund Blended Index      
MFS Lifetime 2030 Fund Blended Index | Average Annual Return, Percent   12.45% 6.04% 7.96%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   4.12% 4.08% 7.08%
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   1.57% 1.97% 5.25%
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   3.35% 2.56% 5.09%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   5.71% 4.23% 7.07%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   8.70% 4.54% 7.07%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   10.81% 5.60% 7.96%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   9.65% 4.53% 6.90%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   10.20% 5.06% 7.44%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   10.48% 5.32% 7.71%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   10.78% 5.59% 7.98%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   10.93% 5.73% 8.11%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2030 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 60.37% Bloomberg U.S. Aggregate Bond Index; 27.73% Standard & Poor's 500 Stock Index; 7.90% MSCI EAFE Index (net div); 2% Bloomberg Commodity Index; and 2% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2030 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 4.87%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 13.69%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (14.85%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2035 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2035 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 40.67% Bloomberg U.S. Aggregate Bond Index; 40.57% Standard & Poor's 500 Stock Index; 12.83% MSCI EAFE Index (net div); 2.97% Bloomberg Commodity Index; and 2.97% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 6.97%. During the period(s) shown in the bar chart, the highest quarterly return was 16.52% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (19.01)% (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 Lifetime 2035 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2035 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2035 Fund Blended Index      
MFS Lifetime 2035 Fund Blended Index | Average Annual Return, Percent   15.16% 8.53% 9.65%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   6.38% 5.95% 8.48%
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   4.08% 4.11% 6.98%
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   4.60% 4.06% 6.34%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   8.04% 6.10% 8.47%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   11.09% 6.41% 8.47%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   13.15% 7.49% 9.37%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   12.00% 6.41% 8.29%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   12.60% 6.94% 8.85%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   12.87% 7.21% 9.12%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   13.15% 7.48% 9.39%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   13.34% 7.64% 9.54%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2035 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 40.67% Bloomberg U.S. Aggregate Bond Index; 40.57% Standard & Poor's 500 Stock Index; 12.83% MSCI EAFE Index (net div); 2.97% Bloomberg Commodity Index; and 2.97% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2035 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 6.97%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 16.52%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (19.01%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2040 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2040 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 51.63% Standard & Poor's 500 Stock Index; 20.67% Bloomberg U.S. Aggregate Bond Index; 19.77% MSCI EAFE Index (net div); 3.97% Bloomberg Commodity Index; and 3.97% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 9.24%. During the period(s) shown in the bar chart, the highest quarterly return was 17.23% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (20.14)% (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 Lifetime 2040 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2040 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2040 Fund Blended Index      
MFS Lifetime 2040 Fund Blended Index | Average Annual Return, Percent   18.05% 10.22% 10.67%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   8.22% 7.11% 9.23%
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   6.06% 5.26% 7.59%
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   5.82% 5.03% 6.95%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   9.88% 7.27% 9.23%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   12.96% 7.58% 9.24%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   15.06% 8.66% 10.13%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   13.92% 7.58% 9.06%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   14.49% 8.12% 9.60%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   14.80% 8.39% 9.88%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   15.04% 8.66% 10.15%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   15.25% 8.82% 10.30%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2040 Fund Blended Index (the Blended Index) consisted of the following indices and approximate weightings: 51.63% Standard & Poor's 500 Stock Index; 20.67% Bloomberg U.S. Aggregate Bond Index; 19.77% MSCI EAFE Index (net div); 3.97% Bloomberg Commodity Index; and 3.97% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2040 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 9.24%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 17.23%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (20.14%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2045 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2045 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 12.75% Bloomberg U.S. Aggregate Bond Index; 54.42% Standard & Poor's 500 Stock Index; 23.87% MSCI EAFE Index (net div); 4.48% Bloomberg Commodity Index; and 4.48% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 10.24%. During the period(s) shown in the bar chart, the highest quarterly return was 17.85% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (21.19)% (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 Lifetime 2045 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2045 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2045 Fund Blended Index      
MFS Lifetime 2045 Fund Blended Index | Average Annual Return, Percent   19.34% 11.05% 11.17%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   8.76% 7.57% 9.54%
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   6.66% 5.79% 8.14%
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   6.20% 5.41% 7.31%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   10.54% 7.74% 9.53%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   13.52% 8.05% 9.53%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   15.68% 9.12% 10.48%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   14.58% 8.04% 9.36%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   15.12% 8.57% 9.91%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   15.40% 8.86% 10.19%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   15.71% 9.14% 10.47%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   15.89% 9.29% 10.62%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2045 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 12.75% Bloomberg U.S. Aggregate Bond Index; 54.42% Standard & Poor's 500 Stock Index; 23.87% MSCI EAFE Index (net div); 4.48% Bloomberg Commodity Index; and 4.48% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2045 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 10.24%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 17.85%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (21.19%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2050 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2050 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 56.92% Standard & Poor's 500 Stock Index; 27.87% MSCI EAFE Index (net div); 5.25% Bloomberg U.S. Aggregate Bond Index; 4.98% Bloomberg Commodity Index; and 4.98% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 10.99%. During the period(s) shown in the bar chart, the highest quarterly return was 17.89% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (21.22)% (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 Lifetime 2050 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2050 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2050 Fund Blended Index      
MFS Lifetime 2050 Fund Blended Index | Average Annual Return, Percent   20.56% 11.50% 11.40%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   9.30% 7.77% 9.64%
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   7.30% 5.99% 8.25%
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   6.54% 5.59% 7.42%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   11.13% 7.95% 9.63%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   14.17% 8.25% 9.63%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   16.33% 9.34% 10.58%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   15.17% 8.25% 9.48%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   15.74% 8.79% 10.03%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   16.03% 9.07% 10.30%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   16.27% 9.33% 10.57%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   16.45% 9.49% 10.72%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2050 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 56.92% Standard & Poor's 500 Stock Index; 27.87% MSCI EAFE Index (net div); 5.25% Bloomberg U.S. Aggregate Bond Index; 4.98% Bloomberg Commodity Index; and 4.98% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2050 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 10.99%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 17.89%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (21.22%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2055 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2055 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 11.08%. During the period(s) shown in the bar chart, the highest quarterly return was 17.91% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (21.17)% (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 Lifetime 2055 Fund
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 14.82%
MFS Lifetime 2055 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2055 Fund Blended Index      
MFS Lifetime 2055 Fund Blended Index | Average Annual Return, Percent   20.56% 11.51% 11.40%
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   9.32% 7.78% 9.64%
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   7.48% 6.11% 8.36%
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   6.44% 5.61% 7.46%
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   11.09% 7.95% 9.63%
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   14.11% 8.25% 9.63%
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   16.29% 9.34% 10.52%
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   15.11% 8.25% 9.46%
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   15.69% 8.80% 10.02%
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   16.04% 9.06% 10.29%
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   16.32% 9.34% 10.57%
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   16.45% 9.50% 10.72%
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2055 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2055 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 11.08%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 17.91%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (21.17%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2060 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2060 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 11.09%. During the period(s) shown in the bar chart, the highest quarterly return was 18.07% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (21.23)% (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 Lifetime 2060 Fund
 12 Months Ended 60 Months Ended 109 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 14.42% 15.22%
Standard & Poor's 500 Stock Index | Performance Inception Date       Dec. 06, 2016
MFS Lifetime 2060 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2060 Fund Blended Index      
MFS Lifetime 2060 Fund Blended Index | Average Annual Return, Percent   20.56% 11.51% 11.91%
MFS Lifetime 2060 Fund Blended Index | Performance Inception Date       Dec. 06, 2016
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class A | Average Annual Return, Percent   9.16% 7.72% 9.80%
Class A | Performance Inception Date       Dec. 06, 2016
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   7.39% 6.25% 8.58%
Class A | After Taxes on Distributions | Performance Inception Date       Dec. 06, 2016
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   6.27% 5.62% 7.56%
Class A | After Taxes on Distributions and Sales | Performance Inception Date       Dec. 06, 2016
Class B | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class B | Average Annual Return, Percent   11.89% 8.18% 9.85%
Class B | Performance Inception Date       Dec. 06, 2016
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class C | Average Annual Return, Percent   14.00% 8.19% 9.81%
Class C | Performance Inception Date       Dec. 06, 2016
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class I | Average Annual Return, Percent   16.13% 9.28% 10.81%
Class I | Performance Inception Date       Dec. 06, 2016
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R1 | Average Annual Return, Percent   15.89% 8.74% 10.01%
Class R1 | Performance Inception Date       Dec. 06, 2016
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R2 | Average Annual Return, Percent   15.53% 8.73% 10.25%
Class R2 | Performance Inception Date       Dec. 06, 2016
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R3 | Average Annual Return, Percent   15.86% 9.01% 10.53%
Class R3 | Performance Inception Date       Dec. 06, 2016
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R4 | Average Annual Return, Percent   16.11% 9.26% 10.79%
Class R4 | Performance Inception Date       Dec. 06, 2016
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes      
Class R6 | Average Annual Return, Percent   16.31% 9.44% 10.94%
Class R6 | Performance Inception Date       Dec. 06, 2016
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2060 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2060 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 11.09%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 18.07%
Highest Quarterly Return, Date Jun. 30, 2020
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (21.23%)
Lowest Quarterly Return, Date Mar. 31, 2020
MFS Lifetime 2065 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.
Performance Additional Market Index [Text] As of December 31, 2025, the MFS Lifetime 2065 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.
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 six-month period ended June 30, 2026, was 11.07%. During the period(s) shown in the bar chart, the highest quarterly return was 10.45% (for the calendar quarter ended December 31, 2023) and the lowest quarterly return was (13.27)% (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 Lifetime 2065 Fund
 12 Months Ended 52 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2025
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   17.88% 11.66%
Standard & Poor's 500 Stock Index | Performance Inception Date     Sep. 01, 2021
MFS Lifetime 2065 Fund Blended Index | Average Annual Return, Label [Optional Text] MFS Lifetime 2065 Fund Blended Index    
MFS Lifetime 2065 Fund Blended Index | Average Annual Return, Percent   20.56% 9.21%
MFS Lifetime 2065 Fund Blended Index | Performance Inception Date     Sep. 01, 2021
Class A | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class A | Average Annual Return, Percent   9.21% 4.96%
Class A | Performance Inception Date     Sep. 01, 2021
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   7.79% 3.64%
Class A | After Taxes on Distributions | Performance Inception Date     Sep. 01, 2021
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   6.10% 3.42%
Class A | After Taxes on Distributions and Sales | Performance Inception Date     Sep. 01, 2021
Class C | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class C | Average Annual Return, Percent   14.01% 5.63%
Class C | Performance Inception Date     Sep. 01, 2021
Class I | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class I | Average Annual Return, Percent   16.14% 6.69%
Class I | Performance Inception Date     Sep. 01, 2021
Class R1 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R1 | Average Annual Return, Percent   15.07% 5.64%
Class R1 | Performance Inception Date     Sep. 01, 2021
Class R2 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R2 | Average Annual Return, Percent   15.62% 6.16%
Class R2 | Performance Inception Date     Sep. 01, 2021
Class R3 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R3 | Average Annual Return, Percent   15.92% 6.42%
Class R3 | Performance Inception Date     Sep. 01, 2021
Class R4 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R4 | Average Annual Return, Percent   16.12% 6.66%
Class R4 | Performance Inception Date     Sep. 01, 2021
Class R6 | Average Annual Return, Label [Optional Text] Returns Before Taxes    
Class R6 | Average Annual Return, Percent   16.37% 6.78%
Class R6 | Performance Inception Date     Sep. 01, 2021
Average Annual Return, Caption [Optional Text] Average Annual Total Returns (For the Periods Ended December 31, 2025)
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]

As of December 31, 2025, the MFS Lifetime 2065 Fund Blended Index (the Blended Index) consisted of the following indices and weightings: 57% Standard & Poor's 500 Stock Index; 28% MSCI EAFE Index (net div); 5% Bloomberg U.S. Aggregate Bond Index; 5% Bloomberg Commodity Index; and 5% FTSE EPRA Nareit Developed Real Estate Index (net div). The components and weightings of the Blended Index may have differed during the periods and may differ in the future. The weightings of the Blended Index are designed to change systematically on a preset schedule and will differ over time.

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 Lifetime 2065 Fund | Class A  
Prospectus [Line Items]  
Year to Date Return, Label [Optional Text] The total return for the six-month period ended
Bar Chart, Year to Date Return 11.07%
Bar Chart, Year to Date Return, Date Jun. 30, 2026
Highest Quarterly Return, Label [Optional Text] highest quarterly return
Highest Quarterly Return 10.45%
Highest Quarterly Return, Date Dec. 31, 2023
Lowest Quarterly Return, Label [Optional Text] lowest quarterly return
Lowest Quarterly Return (13.27%)
Lowest Quarterly Return, Date Jun. 30, 2022