v3.25.2
Fees and Expenses
May 31, 2025
USD ($)
MFS Aggressive Growth Allocation 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 15 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 Aggressive Growth Allocation 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 Aggressive Growth Allocation 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): 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.05%
Acquired Fund Fees and Expenses 0.62% 0.62% 0.62% 0.62% 0.62% 0.62% 0.62% 0.62% 0.62%
Expenses (as a percentage of Assets) 1.00% 1.75% 1.75% 0.75% 1.75% 1.25% 1.00% 0.75% 0.67%
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 Aggressive Growth Allocation 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 $ 671 $ 578 $ 278 $ 77 $ 178 $ 127 $ 102 $ 77 $ 68
Expense Example, with Redemption, 3 Years 875 851 551 240 551 397 318 240 214
Expense Example, with Redemption, 5 Years 1,096 1,149 949 417 949 686 552 417 373
Expense Example, with Redemption, 10 Years $ 1,729 $ 1,864 $ 1,864 $ 930 $ 2,062 $ 1,511 $ 1,225 $ 930 $ 835
[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 Aggressive Growth Allocation Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 178 $ 178
Expense Example, No Redemption, 3 Years [1] 551 551
Expense Example, No Redemption, 5 Years [1] 949 949
Expense Example, No Redemption, 10 Years [1] $ 1,864 $ 1,864
[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 Aggressive Growth Allocation 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 Blended Research Growth Equity 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 have been adjusted to reflect fee arrangements that are effective October 1, 2025.

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 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 $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 Blended Research Growth Equity 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 Blended Research Growth Equity 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) 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25%
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): 0.18% 0.18% 0.18% 0.18% 0.18% 0.18% 0.18% 0.18% 0.11%
Expenses (as a percentage of Assets) 0.68% 1.43% 1.43% 0.43% 1.43% 0.93% 0.68% 0.43% 0.36%
Fee Waiver or Reimbursement [1] (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.03%)
Net Expenses (as a percentage of Assets) 0.64% 1.39% 1.39% 0.39% 1.39% 0.89% 0.64% 0.39% 0.33%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 B, 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 September 30, 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 Blended Research Growth Equity 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 $ 637 $ 542 $ 242 $ 40 $ 142 $ 91 $ 65 $ 40 $ 34
Expense Example, with Redemption, 3 Years 776 749 449 134 449 292 214 134 113
Expense Example, with Redemption, 5 Years 928 978 778 237 778 511 375 237 199
Expense Example, with Redemption, 10 Years $ 1,369 $ 1,505 $ 1,505 $ 538 $ 1,710 $ 1,139 $ 843 $ 538 $ 453
[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 Blended Research Growth Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 142 $ 142
Expense Example, No Redemption, 3 Years [1] 449 449
Expense Example, No Redemption, 5 Years [1] 778 778
Expense Example, No Redemption, 10 Years [1] $ 1,505 $ 1,505
[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 46% of the average value of its portfolio.
Portfolio Turnover, Rate 46.00%
MFS Blended Research Growth Equity 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 Blended Research Mid Cap Equity 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 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 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 $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 Blended Research Mid Cap Equity 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 Blended Research Mid Cap Equity 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) 0.50% 0.50% 0.50% 0.50% 0.50% 0.50% 0.50% 0.50% 0.50%
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): 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.07%
Expenses (as a percentage of Assets) 0.92% 1.67% 1.67% 0.67% 1.67% 1.17% 0.92% 0.67% 0.57%
Fee Waiver or Reimbursement [1] (0.08%) (0.08%) (0.08%) (0.08%) (0.08%) (0.08%) (0.08%) (0.08%) (0.05%)
Net Expenses (as a percentage of Assets) 0.84% 1.59% 1.59% 0.59% 1.59% 1.09% 0.84% 0.59% 0.52%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 0.84% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.59% of the class' average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.59% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.09% of the class' average daily net assets annually for Class R2 shares, and 0.52% 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 September 30, 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 Blended Research Mid Cap Equity 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 $ 656 $ 562 $ 262 $ 60 $ 162 $ 111 $ 86 $ 60 $ 53
Expense Example, with Redemption, 3 Years 844 819 519 206 519 364 285 206 178
Expense Example, with Redemption, 5 Years 1,048 1,100 900 365 900 636 501 365 313
Expense Example, with Redemption, 10 Years $ 1,634 $ 1,770 $ 1,770 $ 827 $ 1,970 $ 1,413 $ 1,124 $ 827 $ 709
[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 Blended Research Mid Cap Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 162 $ 162
Expense Example, No Redemption, 3 Years [1] 519 519
Expense Example, No Redemption, 5 Years [1] 900 900
Expense Example, No Redemption, 10 Years [1] $ 1,770 $ 1,770
[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 58% of the average value of its portfolio.
Portfolio Turnover, Rate 58.00%
MFS Blended Research Mid Cap Equity 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 Blended Research Small Cap Equity 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 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 $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 Blended Research Small Cap Equity 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 Blended Research Small Cap Equity 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) 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65%
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% 0.12%
Expenses (as a percentage of Assets) 1.13% 1.88% 1.88% 0.88% 1.88% 1.38% 1.13% 0.88% 0.77%
Fee Waiver or Reimbursement [1] (0.14%) (0.14%) (0.14%) (0.14%) (0.14%) (0.14%) (0.14%) (0.14%) (0.11%)
Net Expenses (as a percentage of Assets) 0.99% 1.74% 1.74% 0.74% 1.74% 1.24% 0.99% 0.74% 0.66%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 0.99% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.74% of the class' average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.74% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.24% of the class' average daily net assets annually for Class R2 shares, and 0.66% 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 September 30, 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 Blended Research Small Cap Equity 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 $ 670 $ 577 $ 277 $ 76 $ 177 $ 126 $ 101 $ 76 $ 67
Expense Example, with Redemption, 3 Years 900 877 577 267 577 423 345 267 235
Expense Example, with Redemption, 5 Years 1,149 1,203 1,003 474 1,003 742 609 474 417
Expense Example, with Redemption, 10 Years $ 1,859 $ 1,994 $ 1,994 $ 1,071 $ 2,190 $ 1,645 $ 1,362 $ 1,071 $ 944
[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 Blended Research Small Cap Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 177 $ 177
Expense Example, No Redemption, 3 Years [1] 577 577
Expense Example, No Redemption, 5 Years [1] 1,003 1,003
Expense Example, No Redemption, 10 Years [1] $ 1,994 $ 1,994
[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 66% of the average value of its portfolio.
Portfolio Turnover, Rate 66.00%
MFS Blended Research Small Cap Equity 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 Blended Research Value Equity 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 have been adjusted to reflect fee arrangements that are effective October 1, 2025. Expenses 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 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 $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 Blended Research Value Equity 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 Blended Research Value Equity 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) 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25%
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% 0.12%
Expenses (as a percentage of Assets) 0.69% 1.44% 1.44% 0.44% 1.44% 0.94% 0.69% 0.44% 0.37%
Fee Waiver or Reimbursement [1] (0.05%) (0.05%) (0.05%) (0.05%) (0.05%) (0.05%) (0.05%) (0.05%) (0.03%)
Net Expenses (as a percentage of Assets) 0.64% 1.39% 1.39% 0.39% 1.39% 0.89% 0.64% 0.39% 0.34%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 B, 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 0.34% 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 September 30, 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 Blended Research Value Equity 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 $ 637 $ 542 $ 242 $ 40 $ 142 $ 91 $ 65 $ 40 $ 35
Expense Example, with Redemption, 3 Years 778 751 451 136 451 295 216 136 116
Expense Example, with Redemption, 5 Years 932 982 782 241 782 515 379 241 205
Expense Example, with Redemption, 10 Years $ 1,380 $ 1,516 $ 1,516 $ 550 $ 1,720 $ 1,150 $ 854 $ 550 $ 465
[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 Blended Research Value Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 142 $ 142
Expense Example, No Redemption, 3 Years [1] 451 451
Expense Example, No Redemption, 5 Years [1] 782 782
Expense Example, No Redemption, 10 Years [1] $ 1,516 $ 1,516
[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 48% of the average value of its portfolio.
Portfolio Turnover, Rate 48.00%
MFS Blended Research Value Equity 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 Conservative Allocation 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 15 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 Conservative Allocation 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 Conservative Allocation 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): 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 0.03%
Acquired Fund Fees and Expenses 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49%
Expenses (as a percentage of Assets) 0.83% 1.58% 1.58% 0.58% 1.58% 1.08% 0.83% 0.58% 0.52%
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 Conservative Allocation 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 $ 655 $ 561 $ 261 $ 59 $ 161 $ 110 $ 85 $ 59 $ 53
Expense Example, with Redemption, 3 Years 825 799 499 186 499 343 265 186 167
Expense Example, with Redemption, 5 Years 1,009 1,060 860 324 860 595 460 324 291
Expense Example, with Redemption, 10 Years $ 1,541 $ 1,677 $ 1,677 $ 726 $ 1,878 $ 1,317 $ 1,025 $ 726 $ 653
[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 Conservative Allocation Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 161 $ 161
Expense Example, No Redemption, 3 Years [1] 499 499
Expense Example, No Redemption, 5 Years [1] 860 860
Expense Example, No Redemption, 10 Years [1] $ 1,677 $ 1,677
[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 Conservative Allocation 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 Emerging Markets Equity 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 10 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 Emerging Markets Equity 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 Emerging Markets Equity 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) 0.89% 0.89% 0.89% 0.89% 0.89% 0.89% 0.89% 0.89% 0.89%
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%
Expenses (as a percentage of Assets) 1.35% 2.10% 2.10% 1.10% 2.10% 1.60% 1.35% 1.10% 0.96%
Fee Waiver or Reimbursement [1] (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.04%) (0.02%)
Net Expenses (as a percentage of Assets) 1.31% 2.06% 2.06% 1.06% 2.06% 1.56% 1.31% 1.06% 0.94%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 1.31% of the class' average daily net assets annually for each of Class A and Class R3 shares, 2.06% of the class' average daily net assets annually for each of Class B, Class C, and Class R1 shares, 1.06% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.56% of the class' average daily net assets annually for Class R2 shares, and 0.94% 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 September 30, 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 Emerging Markets Equity 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 $ 701 $ 609 $ 309 $ 108 $ 209 $ 159 $ 133 $ 108 $ 96
Expense Example, with Redemption, 3 Years 974 954 654 346 654 501 424 346 304
Expense Example, with Redemption, 5 Years 1,268 1,325 1,125 602 1,125 867 736 602 529
Expense Example, with Redemption, 10 Years $ 2,102 $ 2,236 $ 2,236 $ 1,337 $ 2,428 $ 1,897 $ 1,620 $ 1,337 $ 1,176
[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 Emerging Markets Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 209 $ 209
Expense Example, No Redemption, 3 Years [1] 654 654
Expense Example, No Redemption, 5 Years [1] 1,125 1,125
Expense Example, No Redemption, 10 Years [1] $ 2,236 $ 2,236
[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 36% of the average value of its portfolio.
Portfolio Turnover, Rate 36.00%
MFS Emerging Markets Equity 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 Growth Allocation 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 15 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 Growth Allocation 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 Growth Allocation 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): 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.04%
Acquired Fund Fees and Expenses 0.59% 0.59% 0.59% 0.59% 0.59% 0.59% 0.59% 0.59% 0.59%
Expenses (as a percentage of Assets) 0.95% 1.70% 1.70% 0.70% 1.70% 1.20% 0.95% 0.70% 0.63%
Fee Waiver or Reimbursement [1] (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.02%)
Net Expenses (as a percentage of Assets) 0.94% 1.69% 1.69% 0.69% 1.69% 1.19% 0.94% 0.69% 0.61%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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, such that "Other Expenses" do not exceed 0.10% 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 0.02% 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 September 30, 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 Growth Allocation 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 $ 665 $ 572 $ 272 $ 70 $ 172 $ 121 $ 96 $ 70 $ 62
Expense Example, with Redemption, 3 Years 859 835 535 223 535 380 302 223 200
Expense Example, with Redemption, 5 Years 1,069 1,122 922 389 922 659 525 389 349
Expense Example, with Redemption, 10 Years $ 1,673 $ 1,809 $ 1,809 $ 870 $ 2,008 $ 1,454 $ 1,165 $ 870 $ 784
[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 Growth Allocation Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 172 $ 172
Expense Example, No Redemption, 3 Years [1] 535 535
Expense Example, No Redemption, 5 Years [1] 922 922
Expense Example, No Redemption, 10 Years [1] $ 1,809 $ 1,809
[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 Growth Allocation 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 International Diversification 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 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 $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 International Diversification 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 International Diversification 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): 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.02%
Acquired Fund Fees and Expenses 0.73% 0.73% 0.73% 0.73% 0.73% 0.73% 0.73% 0.73% 0.73%
Expenses (as a percentage of Assets) 1.10% 1.85% 1.85% 0.85% 1.85% 1.35% 1.10% 0.85% 0.75%
Fee Waiver or Reimbursement [1] (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%)
Net Expenses (as a percentage of Assets) 1.08% 1.83% 1.83% 0.83% 1.83% 1.33% 1.08% 0.83% 0.73%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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, such that "Other Expenses" do not exceed 0.10% 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 0.00% 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 September 30, 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 International Diversification 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 $ 679 $ 586 $ 286 $ 85 $ 186 $ 135 $ 110 $ 85 $ 75
Expense Example, with Redemption, 3 Years 903 880 580 269 580 426 348 269 238
Expense Example, with Redemption, 5 Years 1,145 1,199 999 469 999 737 604 469 415
Expense Example, with Redemption, 10 Years $ 1,836 $ 1,971 $ 1,971 $ 1,047 $ 2,168 $ 1,622 $ 1,338 $ 1,047 $ 928
[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 International Diversification Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 186 $ 186
Expense Example, No Redemption, 3 Years [1] 580 580
Expense Example, No Redemption, 5 Years [1] 999 999
Expense Example, No Redemption, 10 Years [1] $ 1,971 $ 1,971
[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 2% of the average value of its portfolio.
Portfolio Turnover, Rate 2.00%
MFS International Diversification 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 International Growth 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 10 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 International Growth 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 International Growth 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) 0.67% 0.67% 0.67% 0.67% 0.67% 0.67% 0.67% 0.67% 0.67%
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): 0.15% 0.15% 0.15% 0.15% 0.15% 0.15% 0.15% 0.15% 0.03%
Expenses (as a percentage of Assets) 1.07% 1.82% 1.82% 0.82% 1.82% 1.32% 1.07% 0.82% 0.70%
Fee Waiver or Reimbursement [1] (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%)
Net Expenses (as a percentage of Assets) 1.06% 1.81% 1.81% 0.81% 1.81% 1.31% 1.06% 0.81% 0.69%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 International Growth 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 $ 677 $ 584 $ 284 $ 83 $ 184 $ 133 $ 108 $ 83 $ 70
Expense Example, with Redemption, 3 Years 895 872 572 261 572 417 339 261 223
Expense Example, with Redemption, 5 Years 1,130 1,184 984 454 984 723 589 454 389
Expense Example, with Redemption, 10 Years $ 1,805 $ 1,940 $ 1,940 $ 1,013 $ 2,136 $ 1,589 $ 1,305 $ 1,013 $ 870
[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 International Growth Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 184 $ 184
Expense Example, No Redemption, 3 Years [1] 572 572
Expense Example, No Redemption, 5 Years [1] 984 984
Expense Example, No Redemption, 10 Years [1] $ 1,940 $ 1,940
[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 20% of the average value of its portfolio.
Portfolio Turnover, Rate 20.00%
MFS International Growth 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 International Intrinsic Value 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 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 $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 International Intrinsic Value 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 International Intrinsic Value 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) 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65% 0.65%
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): 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.13% 0.02%
Expenses (as a percentage of Assets) 1.03% 1.78% 1.78% 0.78% 1.78% 1.28% 1.03% 0.78% 0.67%
Fee Waiver or Reimbursement [1] (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%) (0.01%)
Net Expenses (as a percentage of Assets) 1.02% 1.77% 1.77% 0.77% 1.77% 1.27% 1.02% 0.77% 0.66%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 International Intrinsic Value 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 $ 673 $ 580 $ 280 $ 79 $ 180 $ 129 $ 104 $ 79 $ 67
Expense Example, with Redemption, 3 Years 883 859 559 248 559 405 327 248 213
Expense Example, with Redemption, 5 Years 1,110 1,164 964 432 964 701 568 432 372
Expense Example, with Redemption, 10 Years $ 1,761 $ 1,896 $ 1,896 $ 965 $ 2,094 $ 1,544 $ 1,259 $ 965 $ 834
[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 International Intrinsic Value Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 180 $ 180
Expense Example, No Redemption, 3 Years [1] 559 559
Expense Example, No Redemption, 5 Years [1] 964 964
Expense Example, No Redemption, 10 Years [1] $ 1,896 $ 1,896
[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 International Intrinsic Value 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 International Large Cap Value 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 10 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 International Large Cap Value 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 International Large Cap Value Fund
Class A
Class C
Class I
Class R1
Class R2
Class R3
Class R4
Class R6
Management Fees (as a percentage of Assets) 0.71% 0.71% 0.71% 0.71% 0.71% 0.71% 0.71% 0.71%
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): 0.06% 0.06% 0.06% 0.06% 0.06% 0.06% 0.06% 0.03%
Expenses (as a percentage of Assets) 1.02% 1.77% 0.77% 1.77% 1.27% 1.02% 0.77% 0.74%
Fee Waiver or Reimbursement [1] (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.07%)
Net Expenses (as a percentage of Assets) 0.96% 1.71% 0.71% 1.71% 1.21% 0.96% 0.71% 0.67%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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 0.96% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.71% of the class' average daily net assets annually for each of Class C and Class R1 shares, 0.71% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.21% of the class' average daily net assets annually for Class R2 shares, and 0.67% 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 September 30, 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 International Large Cap Value 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 $ 667 $ 274 $ 73 $ 174 $ 123 $ 98 $ 73 $ 68
Expense Example, with Redemption, 3 Years 875 551 240 551 397 319 240 230
Expense Example, with Redemption, 5 Years 1,100 954 422 954 691 557 422 405
Expense Example, with Redemption, 10 Years $ 1,746 $ 1,881 $ 949 $ 2,079 $ 1,529 $ 1,242 $ 949 $ 912
[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 International Large Cap Value Fund
Class C
USD ($)
 [1]
Expense Example, No Redemption, 1 Year $ 174
Expense Example, No Redemption, 3 Years 551
Expense Example, No Redemption, 5 Years 954
Expense Example, No Redemption, 10 Years $ 1,881
[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 International Large Cap Value 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 Managed Wealth 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 13 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 Managed Wealth 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 Managed Wealth 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) 0.35% 0.35% 0.35% 0.35% 0.35% 0.35% 0.35% 0.35% 0.35%
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): 0.84% 0.84% 0.84% 0.84% 0.84% 0.84% 0.84% 0.84% 0.77%
Acquired Fund Fees and Expenses 0.47% 0.47% 0.47% 0.47% 0.47% 0.47% 0.47% 0.47% 0.47%
Expenses (as a percentage of Assets) 1.91% 2.66% 2.66% 1.66% 2.66% 2.16% 1.91% 1.66% 1.59%
Fee Waiver or Reimbursement [1] (0.52%) (0.52%) (0.52%) (0.52%) (0.52%) (0.52%) (0.52%) (0.52%) (0.48%)
Net Expenses (as a percentage of Assets) 1.39% 2.14% 2.14% 1.14% 2.14% 1.64% 1.39% 1.14% 1.11%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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 September 30, 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, and fees and expenses associated with investments in investment companies and other similar investment vehicles), such that "Total Annual Fund Operating Expenses" do not exceed 0.91% of the class' average daily net assets annually for each of Class A and Class R3 shares, 1.66% of the class' average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.66% of the class' average daily net assets annually for each of Class I and Class R4 shares, 1.16% of the class' average daily net assets annually for Class R2 shares, and 0.63% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.01% of interest and/or investment-related expenses incurred in connection with the fund's investment activity which are excluded from the expense limitation described in the prior sentence.) This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 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 Managed Wealth 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 $ 708 $ 617 $ 317 $ 116 $ 217 $ 167 $ 142 $ 116 $ 113
Expense Example, with Redemption, 3 Years 1,093 1,077 777 473 777 626 550 473 455
Expense Example, with Redemption, 5 Years 1,502 1,564 1,364 853 1,364 1,112 983 853 820
Expense Example, with Redemption, 10 Years $ 2,640 $ 2,773 $ 2,773 $ 1,922 $ 2,955 $ 2,452 $ 2,191 $ 1,922 $ 1,849
[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 Managed Wealth Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 217 $ 217
Expense Example, No Redemption, 3 Years [1] 777 777
Expense Example, No Redemption, 5 Years [1] 1,364 1,364
Expense Example, No Redemption, 10 Years [1] $ 2,773 $ 2,773
[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 11% of the average value of its portfolio.
Portfolio Turnover, Rate 11.00%
MFS Managed Wealth 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 Moderate Allocation 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 15 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 Moderate Allocation 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 Moderate Allocation 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): 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.03%
Acquired Fund Fees and Expenses 0.54% 0.54% 0.54% 0.54% 0.54% 0.54% 0.54% 0.54% 0.54%
Expenses (as a percentage of Assets) 0.89% 1.64% 1.64% 0.64% 1.64% 1.14% 0.89% 0.64% 0.57%
Fee Waiver or Reimbursement [1] 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% (0.01%)
Net Expenses (as a percentage of Assets) 0.89% 1.64% 1.64% 0.64% 1.64% 1.14% 0.89% 0.64% 0.56%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 2026 September 30, 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, such that "Other Expenses" do not exceed 0.10% 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 0.02% 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 September 30, 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 Moderate Allocation 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 $ 661 $ 567 $ 267 $ 65 $ 167 $ 116 $ 91 $ 65 $ 57
Expense Example, with Redemption, 3 Years 843 817 517 205 517 362 284 205 182
Expense Example, with Redemption, 5 Years 1,040 1,092 892 357 892 628 493 357 317
Expense Example, with Redemption, 10 Years $ 1,608 $ 1,743 $ 1,743 $ 798 $ 1,944 $ 1,386 $ 1,096 $ 798 $ 713
[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 Moderate Allocation Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 167 $ 167
Expense Example, No Redemption, 3 Years [1] 517 517
Expense Example, No Redemption, 5 Years [1] 892 892
Expense Example, No Redemption, 10 Years [1] $ 1,743 $ 1,743
[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 6% of the average value of its portfolio.
Portfolio Turnover, Rate 6.00%
MFS Moderate Allocation 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.