v3.25.2
Fees and Expenses
Apr. 30, 2025
USD ($)
MFS Core Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 11 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Core Bond Fund
Class A
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Core Bond Fund
Class A
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.33% 0.33% 0.33% 0.33% 0.33% 0.33% 0.33% 0.33%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.93% 0.93% 0.93% 0.93% 0.93% 0.93% 0.93% 0.90%
Expenses (as a percentage of Assets) 1.51% 2.26% 1.26% 2.26% 1.76% 1.51% 1.26% 1.23%
Fee Waiver or Reimbursement [1] (0.87%) (0.87%) (0.87%) (0.87%) (0.87%) (0.87%) (0.87%) (0.90%)
Net Expenses (as a percentage of Assets) 0.64% 1.39% 0.39% 1.39% 0.89% 0.64% 0.39% 0.33%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to waive at least 0.01% of the fund's management fee as part of an agreement pursuant to which MFS has agreed to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026. MFS has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, certain tax reclaim recovery expenses (including contingency fees and closing agreement expenses), and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.64% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.39% of the class' average daily net assets annually for each of Class C and Class R1 shares, 0.39% of the class' average daily net assets annually for each of Class I and Class R4 shares, 0.89% of the class' average daily net assets annually for Class R2 shares, and 0.33% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Core Bond Fund - USD ($)
Class A
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 488 $ 242 $ 40 $ 142 $ 91 $ 65 $ 40 $ 34
Expense Example, with Redemption, 3 Years 800 623 313 623 469 392 313 301
Expense Example, with Redemption, 5 Years 1,135 1,131 608 1,131 873 741 608 589
Expense Example, with Redemption, 10 Years $ 2,079 $ 2,337 $ 1,446 $ 2,528 $ 2,001 $ 1,727 $ 1,446 $ 1,409
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Core Bond Fund
Class C
USD ($)
 [1]
Expense Example, No Redemption, 1 Year $ 142
Expense Example, No Redemption, 3 Years 623
Expense Example, No Redemption, 5 Years 1,131
Expense Example, No Redemption, 10 Years $ 2,337
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 139% of the average value of its portfolio (40% excluding to be announced (TBA) transactions).
Portfolio Turnover, Rate 139.00%
MFS Core Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime Income Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime Income Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime Income Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.08%
Acquired Fund Fees and Expenses 0.44% 0.44% 0.44% 0.44% 0.44% 0.44% 0.44% 0.44% 0.44%
Expenses (as a percentage of Assets) 0.88% 1.63% 1.63% 0.63% 1.63% 1.13% 0.88% 0.63% 0.52%
Fee Waiver or Reimbursement [1] (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.20%)
Net Expenses (as a percentage of Assets) 0.69% 1.44% 1.44% 0.44% 1.44% 0.94% 0.69% 0.44% 0.32%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.12)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime Income Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 492 $ 547 $ 247 $ 45 $ 147 $ 96 $ 70 $ 45 $ 33
Expense Example, with Redemption, 3 Years 676 796 496 183 496 340 262 183 147
Expense Example, with Redemption, 5 Years 874 1,069 869 332 869 604 469 332 271
Expense Example, with Redemption, 10 Years $ 1,446 $ 1,716 $ 1,716 $ 768 $ 1,917 $ 1,358 $ 1,067 $ 768 $ 633
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime Income Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 147 $ 147
Expense Example, No Redemption, 3 Years [1] 496 496
Expense Example, No Redemption, 5 Years [1] 869 869
Expense Example, No Redemption, 10 Years [1] $ 1,716 $ 1,716
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 5% of the average value of its portfolio.
Portfolio Turnover, Rate 5.00%
MFS Lifetime Income Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2025 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2025 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2025 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.09%
Acquired Fund Fees and Expenses 0.45% 0.45% 0.45% 0.45% 0.45% 0.45% 0.45% 0.45% 0.45%
Expenses (as a percentage of Assets) 0.93% 1.68% 1.68% 0.68% 1.68% 1.18% 0.93% 0.68% 0.54%
Fee Waiver or Reimbursement [1] (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%)
Net Expenses (as a percentage of Assets) 0.70% 1.45% 1.45% 0.45% 1.45% 0.95% 0.70% 0.45% 0.31%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2025 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 642 $ 548 $ 248 $ 46 $ 148 $ 97 $ 72 $ 46 $ 32
Expense Example, with Redemption, 3 Years 833 807 507 194 507 352 273 194 150
Expense Example, with Redemption, 5 Years 1,039 1,091 891 356 891 627 492 356 279
Expense Example, with Redemption, 10 Years $ 1,632 $ 1,768 $ 1,768 $ 825 $ 1,968 $ 1,411 $ 1,122 $ 825 $ 655
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2025 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 148 $ 148
Expense Example, No Redemption, 3 Years [1] 507 507
Expense Example, No Redemption, 5 Years [1] 891 891
Expense Example, No Redemption, 10 Years [1] $ 1,768 $ 1,768
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 9% of the average value of its portfolio.
Portfolio Turnover, Rate 9.00%
MFS Lifetime 2025 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2030 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2030 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2030 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.19% 0.06%
Acquired Fund Fees and Expenses 0.48% 0.48% 0.48% 0.48% 0.48% 0.48% 0.48% 0.48% 0.48%
Expenses (as a percentage of Assets) 0.92% 1.67% 1.67% 0.67% 1.67% 1.17% 0.92% 0.67% 0.54%
Fee Waiver or Reimbursement [1] (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.19%) (0.20%)
Net Expenses (as a percentage of Assets) 0.73% 1.48% 1.48% 0.48% 1.48% 0.98% 0.73% 0.48% 0.34%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2030 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 645 $ 551 $ 251 $ 49 $ 151 $ 100 $ 75 $ 49 $ 35
Expense Example, with Redemption, 3 Years 834 808 508 195 508 353 274 195 153
Expense Example, with Redemption, 5 Years 1,038 1,090 890 354 890 625 491 354 282
Expense Example, with Redemption, 10 Years $ 1,625 $ 1,760 $ 1,760 $ 817 $ 1,960 $ 1,403 $ 1,114 $ 817 $ 658
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2030 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 151 $ 151
Expense Example, No Redemption, 3 Years [1] 508 508
Expense Example, No Redemption, 5 Years [1] 890 890
Expense Example, No Redemption, 10 Years [1] $ 1,760 $ 1,760
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 9% of the average value of its portfolio.
Portfolio Turnover, Rate 9.00%
MFS Lifetime 2030 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2035 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2035 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2035 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.21% 0.21% 0.21% 0.21% 0.21% 0.21% 0.21% 0.21% 0.07%
Acquired Fund Fees and Expenses 0.52% 0.52% 0.52% 0.52% 0.52% 0.52% 0.52% 0.52% 0.52%
Expenses (as a percentage of Assets) 0.98% 1.73% 1.73% 0.73% 1.73% 1.23% 0.98% 0.73% 0.59%
Fee Waiver or Reimbursement [1] (0.21%) (0.21%) (0.21%) (0.21%) (0.21%) (0.21%) (0.21%) (0.21%) (0.21%)
Net Expenses (as a percentage of Assets) 0.77% 1.52% 1.52% 0.52% 1.52% 1.02% 0.77% 0.52% 0.38%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2035 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 649 $ 555 $ 255 $ 53 $ 155 $ 104 $ 79 $ 53 $ 39
Expense Example, with Redemption, 3 Years 849 824 524 212 524 370 291 212 168
Expense Example, with Redemption, 5 Years 1,066 1,119 919 385 919 655 521 385 308
Expense Example, with Redemption, 10 Years $ 1,689 $ 1,825 $ 1,825 $ 887 $ 2,024 $ 1,470 $ 1,182 $ 887 $ 718
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2035 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 155 $ 155
Expense Example, No Redemption, 3 Years [1] 524 524
Expense Example, No Redemption, 5 Years [1] 919 919
Expense Example, No Redemption, 10 Years [1] $ 1,825 $ 1,825
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.
Portfolio Turnover, Rate 14.00%
MFS Lifetime 2035 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2040 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2040 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2040 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.06%
Acquired Fund Fees and Expenses 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56%
Expenses (as a percentage of Assets) 1.01% 1.76% 1.76% 0.76% 1.76% 1.26% 1.01% 0.76% 0.62%
Fee Waiver or Reimbursement [1] (0.20%) (0.20%) (0.20%) (0.20%) (0.20%) (0.20%) (0.20%) (0.20%) (0.20%)
Net Expenses (as a percentage of Assets) 0.81% 1.56% 1.56% 0.56% 1.56% 1.06% 0.81% 0.56% 0.42%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2040 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 653 $ 559 $ 259 $ 57 $ 159 $ 108 $ 83 $ 57 $ 43
Expense Example, with Redemption, 3 Years 859 835 535 223 535 380 302 223 178
Expense Example, with Redemption, 5 Years 1,082 1,135 935 403 935 672 538 403 326
Expense Example, with Redemption, 10 Years $ 1,723 $ 1,858 $ 1,858 $ 924 $ 2,057 $ 1,505 $ 1,218 $ 924 $ 755
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2040 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 159 $ 159
Expense Example, No Redemption, 3 Years [1] 535 535
Expense Example, No Redemption, 5 Years [1] 935 935
Expense Example, No Redemption, 10 Years [1] $ 1,858 $ 1,858
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate 13.00%
MFS Lifetime 2040 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2045 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2045 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2045 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.08%
Acquired Fund Fees and Expenses 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56% 0.56%
Expenses (as a percentage of Assets) 1.04% 1.79% 1.79% 0.79% 1.79% 1.29% 1.04% 0.79% 0.64%
Fee Waiver or Reimbursement [1] (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.22%)
Net Expenses (as a percentage of Assets) 0.81% 1.56% 1.56% 0.56% 1.56% 1.06% 0.81% 0.56% 0.42%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2045 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 653 $ 559 $ 259 $ 57 $ 159 $ 108 $ 83 $ 57 $ 43
Expense Example, with Redemption, 3 Years 865 841 541 229 541 386 308 229 183
Expense Example, with Redemption, 5 Years 1,095 1,148 948 416 948 686 552 416 335
Expense Example, with Redemption, 10 Years $ 1,753 $ 1,889 $ 1,889 $ 956 $ 2,086 $ 1,536 $ 1,250 $ 956 $ 777
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2045 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 159 $ 159
Expense Example, No Redemption, 3 Years [1] 541 541
Expense Example, No Redemption, 5 Years [1] 948 948
Expense Example, No Redemption, 10 Years [1] $ 1,889 $ 1,889
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.
Portfolio Turnover, Rate 14.00%
MFS Lifetime 2045 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2050 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2050 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2050 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.23% 0.08%
Acquired Fund Fees and Expenses 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57%
Expenses (as a percentage of Assets) 1.05% 1.80% 1.80% 0.80% 1.80% 1.30% 1.05% 0.80% 0.65%
Fee Waiver or Reimbursement [1] (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.23%) (0.22%)
Net Expenses (as a percentage of Assets) 0.82% 1.57% 1.57% 0.57% 1.57% 1.07% 0.82% 0.57% 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2050 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 654 $ 560 $ 260 $ 58 $ 160 $ 109 $ 84 $ 58 $ 44
Expense Example, with Redemption, 3 Years 868 844 544 232 544 389 311 232 186
Expense Example, with Redemption, 5 Years 1,100 1,153 953 422 953 691 557 422 340
Expense Example, with Redemption, 10 Years $ 1,764 $ 1,899 $ 1,899 $ 968 $ 2,097 $ 1,548 $ 1,262 $ 968 $ 790
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2050 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 160 $ 160
Expense Example, No Redemption, 3 Years [1] 544 544
Expense Example, No Redemption, 5 Years [1] 953 953
Expense Example, No Redemption, 10 Years [1] $ 1,899 $ 1,899
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate 13.00%
MFS Lifetime 2050 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2055 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2055 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2055 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.26% 0.26% 0.26% 0.26% 0.26% 0.26% 0.26% 0.26% 0.11%
Acquired Fund Fees and Expenses 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57%
Expenses (as a percentage of Assets) 1.08% 1.83% 1.83% 0.83% 1.83% 1.33% 1.08% 0.83% 0.68%
Fee Waiver or Reimbursement [1] (0.26%) (0.26%) (0.26%) (0.26%) (0.26%) (0.26%) (0.26%) (0.26%) (0.25%)
Net Expenses (as a percentage of Assets) 0.82% 1.57% 1.57% 0.57% 1.57% 1.07% 0.82% 0.57% 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2055 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 654 $ 560 $ 260 $ 58 $ 160 $ 109 $ 84 $ 58 $ 44
Expense Example, with Redemption, 3 Years 874 850 550 239 550 396 318 239 192
Expense Example, with Redemption, 5 Years 1,113 1,166 966 435 966 704 570 435 354
Expense Example, with Redemption, 10 Years $ 1,794 $ 1,930 $ 1,930 $ 1,001 $ 2,127 $ 1,579 $ 1,294 $ 1,001 $ 823
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2055 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 160 $ 160
Expense Example, No Redemption, 3 Years [1] 550 550
Expense Example, No Redemption, 5 Years [1] 966 966
Expense Example, No Redemption, 10 Years [1] $ 1,930 $ 1,930
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.
Portfolio Turnover, Rate 15.00%
MFS Lifetime 2055 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2060 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below. Expenses for Class B and for Class R1 shares have been adjusted to reflect the full impact of the distribution fee.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2060 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2060 Fund
Class A
Class B
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.34% 0.34% 0.34% 0.34% 0.34% 0.34% 0.34% 0.34% 0.19%
Acquired Fund Fees and Expenses 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57%
Expenses (as a percentage of Assets) 1.16% 1.91% 1.91% 0.91% 1.91% 1.41% 1.16% 0.91% 0.76%
Fee Waiver or Reimbursement [1] (0.34%) (0.34%) (0.34%) (0.34%) (0.34%) (0.34%) (0.34%) (0.34%) (0.33%)
Net Expenses (as a percentage of Assets) 0.82% 1.57% 1.57% 0.57% 1.57% 1.07% 0.82% 0.57% 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class B, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2060 Fund - USD ($)
Class A
Class B
 [1]
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 654 $ 560 $ 260 $ 58 $ 160 $ 109 $ 84 $ 58 $ 44
Expense Example, with Redemption, 3 Years 891 867 567 256 567 413 335 256 210
Expense Example, with Redemption, 5 Years 1,146 1,200 1,000 471 1,000 739 606 471 390
Expense Example, with Redemption, 10 Years $ 1,874 $ 2,009 $ 2,009 $ 1,088 $ 2,205 $ 1,661 $ 1,379 $ 1,088 $ 911
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2060 Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 160 $ 160
Expense Example, No Redemption, 3 Years [1] 567 567
Expense Example, No Redemption, 5 Years [1] 1,000 1,000
Expense Example, No Redemption, 10 Years [1] $ 2,009 $ 2,009
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 18% of the average value of its portfolio.
Portfolio Turnover, Rate 18.00%
MFS Lifetime 2060 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Lifetime 2065 Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS Lifetime 2065 Fund
Class A
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 5.75% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 1.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
[1] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
Operating Expenses Caption [Optional Text] Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Annual Fund Operating Expenses [Table]
Annual Fund Operating Expenses - MFS Lifetime 2065 Fund
Class A
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 1.21% 1.21% 1.21% 1.21% 1.21% 1.21% 1.21% 1.08%
Acquired Fund Fees and Expenses 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57% 0.57%
Expenses (as a percentage of Assets) 2.03% 2.78% 1.78% 2.78% 2.28% 2.03% 1.78% 1.65%
Fee Waiver or Reimbursement [1] (1.21%) (1.21%) (1.21%) (1.21%) (1.21%) (1.21%) (1.21%) (1.22%)
Net Expenses (as a percentage of Assets) 0.82% 1.57% 0.57% 1.57% 1.07% 0.82% 0.57% 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026 August 31, 2026
[1] Massachusetts Financial Services Company (MFS) has agreed in writing to bear the fund's expenses, excluding management fees, distribution and service fees, interest, taxes, extraordinary expenses, brokerage and transaction costs, investment-related expenses, and fees and expenses associated with investments in investment companies and other similar investment vehicles, or make payment to the fund, such that "Other Expenses" do not exceed 0.00% of the class' average daily net assets annually for each of Class A, Class C, Class I, Class R1, Class R2, Class R3, and Class R4 shares, and (0.14)% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least August 31, 2026.
Expense Example [Heading] Example
Expense Example Narrative [Text Block]

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

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Expense Example by, Year, Caption [Text] Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
Expense Example, With Redemption [Table]
Expense Example - MFS Lifetime 2065 Fund - USD ($)
Class A
Class C
 [1]
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Expense Example, with Redemption, 1 Year $ 654 $ 260 $ 58 $ 160 $ 109 $ 84 $ 58 $ 44
Expense Example, with Redemption, 3 Years 1,064 748 442 748 596 519 442 401
Expense Example, with Redemption, 5 Years 1,500 1,362 851 1,362 1,110 981 851 782
Expense Example, with Redemption, 10 Years $ 2,706 $ 2,840 $ 1,994 $ 3,021 $ 2,521 $ 2,261 $ 1,994 $ 1,852
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS Lifetime 2065 Fund
Class C
USD ($)
 [1]
Expense Example, No Redemption, 1 Year $ 160
Expense Example, No Redemption, 3 Years 748
Expense Example, No Redemption, 5 Years 1,362
Expense Example, No Redemption, 10 Years $ 2,840
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 22% of the average value of its portfolio.
Portfolio Turnover, Rate 22.00%
MFS Lifetime 2065 Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.