v3.26.3
Fees and Expenses
May 31, 2026
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): 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.12% 0.04%
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) 0.99% 1.74% 1.74% 0.74% 1.74% 1.24% 0.99% 0.74% 0.66%
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 $ 670 $ 577 $ 277 $ 76 $ 177 $ 126 $ 101 $ 76 $ 67
Expense Example, with Redemption, 3 Years 872 848 548 237 548 393 315 237 211
Expense Example, with Redemption, 5 Years 1,091 1,144 944 411 944 681 547 411 368
Expense Example, with Redemption, 10 Years $ 1,718 $ 1,853 $ 1,853 $ 918 $ 2,052 $ 1,500 $ 1,213 $ 918 $ 822
[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] $ 177 $ 177
Expense Example, No Redemption, 3 Years [1] 548 548
Expense Example, No Redemption, 5 Years [1] 944 944
Expense Example, No Redemption, 10 Years [1] $ 1,853 $ 1,853
[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 1% of the average value of its portfolio.
Portfolio Turnover, Rate 1.00%
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): 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.17% 0.09%
Expenses (as a percentage of Assets) 0.67% 1.42% 1.42% 0.42% 1.42% 0.92% 0.67% 0.42% 0.34%
Fee Waiver or Reimbursement [1] (0.03%) (0.03%) (0.03%) (0.03%) (0.03%) (0.03%) (0.03%) (0.03%) (0.01%)
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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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, 2027.
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 774 746 446 132 446 290 211 132 108
Expense Example, with Redemption, 5 Years 924 973 773 232 773 506 370 232 190
Expense Example, with Redemption, 10 Years $ 1,359 $ 1,495 $ 1,495 $ 527 $ 1,699 $ 1,129 $ 832 $ 527 $ 430
[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] 446 446
Expense Example, No Redemption, 5 Years [1] 773 773
Expense Example, No Redemption, 10 Years [1] $ 1,495 $ 1,495
[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 52% of the average value of its portfolio.
Portfolio Turnover, Rate 52.00%
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 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): 0.22% 0.22% 0.22% 0.22% 0.22% 0.22% 0.22% 0.22% 0.12%
Expenses (as a percentage of Assets) 1.12% 1.87% 1.87% 0.87% 1.87% 1.37% 1.12% 0.87% 0.77%
Fee Waiver or Reimbursement [1] (0.13%) (0.13%) (0.13%) (0.13%) (0.13%) (0.13%) (0.13%) (0.13%) (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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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, 2027.
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 898 875 575 265 575 421 343 265 235
Expense Example, with Redemption, 5 Years 1,145 1,199 999 469 999 738 604 469 417
Expense Example, with Redemption, 10 Years $ 1,849 $ 1,984 $ 1,984 $ 1,061 $ 2,180 $ 1,635 $ 1,352 $ 1,061 $ 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] 575 575
Expense Example, No Redemption, 5 Years [1] 999 999
Expense Example, No Redemption, 10 Years [1] $ 1,984 $ 1,984
[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 73% of the average value of its portfolio.
Portfolio Turnover, Rate 73.00%
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 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) 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49% 0.49%
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): 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.05%
Expenses (as a percentage of Assets) 0.88% 1.63% 1.63% 0.63% 1.63% 1.13% 0.88% 0.63% 0.54%
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) 0.84% 1.59% 1.59% 0.59% 1.59% 1.09% 0.84% 0.59% 0.51%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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 0.51% 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, 2027.
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 $ 52
Expense Example, with Redemption, 3 Years 836 810 510 198 510 355 277 198 170
Expense Example, with Redemption, 5 Years 1,031 1,083 883 347 883 618 484 347 299
Expense Example, with Redemption, 10 Years $ 1,594 $ 1,729 $ 1,729 $ 783 $ 1,929 $ 1,371 $ 1,081 $ 783 $ 674
[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] 510 510
Expense Example, No Redemption, 5 Years [1] 883 883
Expense Example, No Redemption, 10 Years [1] $ 1,729 $ 1,729
[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 51% of the average value of its portfolio.
Portfolio Turnover, Rate 51.00%
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 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 current fee arrangements. 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): 0.18% 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%) (0.02%)
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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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, 2027.
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 776 749 449 134 449 292 214 134 114
Expense Example, with Redemption, 5 Years 928 978 778 237 778 511 375 237 200
Expense Example, with Redemption, 10 Years $ 1,369 $ 1,505 $ 1,505 $ 538 $ 1,710 $ 1,139 $ 843 $ 538 $ 454
[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] 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 50% of the average value of its portfolio.
Portfolio Turnover, Rate 50.00%
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 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS 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 4% of the average value of its portfolio.
Portfolio Turnover, Rate 4.00%
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 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 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) 0.88% 0.88% 0.88% 0.88% 0.88% 0.88% 0.88% 0.88% 0.88%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 1.00% 0.50% 0.25% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.20% 0.07%
Expenses (as a percentage of Assets) 1.33% 2.08% 2.08% 1.08% 2.08% 1.58% 1.33% 1.08% 0.95%
Fee Waiver or Reimbursement [1] (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.02%) (0.01%)
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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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, 2027.
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 970 950 650 341 650 497 419 341 302
Expense Example, with Redemption, 5 Years 1,260 1,317 1,117 594 1,117 859 727 594 525
Expense Example, with Redemption, 10 Years $ 2,083 $ 2,217 $ 2,217 $ 1,315 $ 2,409 $ 1,877 $ 1,600 $ 1,315 $ 1,165
[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] 650 650
Expense Example, No Redemption, 5 Years [1] 1,117 1,117
Expense Example, No Redemption, 10 Years [1] $ 2,217 $ 2,217
[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 45% of the average value of its portfolio.
Portfolio Turnover, Rate 45.00%
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 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS 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): 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.10% 0.03%
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) 0.94% 1.69% 1.69% 0.69% 1.69% 1.19% 0.94% 0.69% 0.62%
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) 0.94% 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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027.
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 857 833 533 221 533 378 300 221 198
Expense Example, with Redemption, 5 Years 1,065 1,118 918 384 918 654 520 384 345
Expense Example, with Redemption, 10 Years $ 1,663 $ 1,799 $ 1,799 $ 859 $ 1,998 $ 1,443 $ 1,155 $ 859 $ 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.
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] 533 533
Expense Example, No Redemption, 5 Years [1] 918 918
Expense Example, No Redemption, 10 Years [1] $ 1,799 $ 1,799
[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 3% of the average value of its portfolio.
Portfolio Turnover, Rate 3.00%
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): 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.11% 0.01%
Acquired Fund Fees and Expenses 0.72% 0.72% 0.72% 0.72% 0.72% 0.72% 0.72% 0.72% 0.72%
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 [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) 1.07% 1.82% 1.82% 0.82% 1.82% 1.32% 1.07% 0.82% 0.72%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027.
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 $ 678 $ 585 $ 285 $ 84 $ 185 $ 134 $ 109 $ 84 $ 74
Expense Example, with Redemption, 3 Years 898 875 575 264 575 420 342 264 232
Expense Example, with Redemption, 5 Years 1,135 1,189 989 460 989 728 595 460 405
Expense Example, with Redemption, 10 Years $ 1,816 $ 1,950 $ 1,950 $ 1,024 $ 2,147 $ 1,601 $ 1,316 $ 1,024 $ 906
[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] $ 185 $ 185
Expense Example, No Redemption, 3 Years [1] 575 575
Expense Example, No Redemption, 5 Years [1] 989 989
Expense Example, No Redemption, 10 Years [1] $ 1,950 $ 1,950
[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 1% of the average value of its portfolio.
Portfolio Turnover, Rate 1.00%
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) 0.66% 0.66% 0.66% 0.66% 0.66% 0.66% 0.66% 0.66% 0.66%
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): 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.14% 0.03%
Expenses (as a percentage of Assets) 1.05% 1.80% 1.80% 0.80% 1.80% 1.30% 1.05% 0.80% 0.69%
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) 1.04% 1.79% 1.79% 0.79% 1.79% 1.29% 1.04% 0.79% 0.68%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027.
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 $ 675 $ 582 $ 282 $ 81 $ 182 $ 131 $ 106 $ 81 $ 69
Expense Example, with Redemption, 3 Years 889 865 565 254 565 411 333 254 220
Expense Example, with Redemption, 5 Years 1,120 1,174 974 443 974 712 578 443 383
Expense Example, with Redemption, 10 Years $ 1,783 $ 1,918 $ 1,918 $ 989 $ 2,115 $ 1,567 $ 1,282 $ 989 $ 858
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
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] $ 182 $ 182
Expense Example, No Redemption, 3 Years [1] 565 565
Expense Example, No Redemption, 5 Years [1] 974 974
Expense Example, No Redemption, 10 Years [1] $ 1,918 $ 1,918
[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 16% of the average value of its portfolio.
Portfolio Turnover, Rate 16.00%
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 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 International Intrinsic 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 International Intrinsic 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) 0.64% 0.64% 0.64% 0.64% 0.64% 0.64% 0.64% 0.64% 0.64%
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% 0.01%
Expenses (as a percentage of Assets) 1.00% 1.75% 1.75% 0.75% 1.75% 1.25% 1.00% 0.75% 0.65%
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) 0.99% 1.74% 1.74% 0.74% 1.74% 1.24% 0.99% 0.74% 0.64%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027.
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 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 $ 65
Expense Example, with Redemption, 3 Years 874 850 550 239 550 396 317 239 207
Expense Example, with Redemption, 5 Years 1,095 1,148 948 416 948 685 551 416 361
Expense Example, with Redemption, 10 Years $ 1,728 $ 1,863 $ 1,863 $ 929 $ 2,062 $ 1,510 $ 1,224 $ 929 $ 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.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - MFS International Intrinsic Equity Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 177 $ 177
Expense Example, No Redemption, 3 Years [1] 550 550
Expense Example, No Redemption, 5 Years [1] 948 948
Expense Example, No Redemption, 10 Years [1] $ 1,863 $ 1,863
[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 21% of the average value of its portfolio.
Portfolio Turnover, Rate 21.00%
MFS International Intrinsic 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 International 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. Expenses have been adjusted to reflect current fee arrangements.

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 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 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) 0.67% 0.67% 0.67% 0.67% 0.67% 0.67% 0.67% 0.67%
Distribution and Service (12b-1) Fees 0.25% 1.00% 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% 0.03%
Expenses (as a percentage of Assets) 1.02% 1.77% 0.77% 1.77% 1.27% 1.02% 0.77% 0.70%
Fee Waiver or Reimbursement [1] (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.06%) (0.03%)
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, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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, 2027.
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 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 875 551 240 551 397 319 240 221
Expense Example, with Redemption, 5 Years 1,100 954 422 954 691 557 422 387
Expense Example, with Redemption, 10 Years $ 1,746 $ 1,881 $ 949 $ 2,079 $ 1,529 $ 1,242 $ 949 $ 868
[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 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 23% of the average value of its portfolio.
Portfolio Turnover, Rate 23.00%
MFS International 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): 0.87% 0.87% 0.87% 0.87% 0.87% 0.87% 0.87% 0.87% 0.78%
Acquired Fund Fees and Expenses 0.46% 0.46% 0.46% 0.46% 0.46% 0.46% 0.46% 0.46% 0.46%
Expenses (as a percentage of Assets) 1.93% 2.68% 2.68% 1.68% 2.68% 2.18% 1.93% 1.68% 1.59%
Fee Waiver or Reimbursement [1] (0.55%) (0.55%) (0.55%) (0.55%) (0.55%) (0.55%) (0.55%) (0.55%) (0.51%)
Net Expenses (as a percentage of Assets) 1.38% 2.13% 2.13% 1.13% 2.13% 1.63% 1.38% 1.13% 1.08%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027. 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 0.61% 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, 2027.
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 $ 707 $ 616 $ 316 $ 115 $ 216 $ 166 $ 141 $ 115 $ 110
Expense Example, with Redemption, 3 Years 1,096 1,080 780 476 780 629 553 476 452
Expense Example, with Redemption, 5 Years 1,509 1,571 1,371 861 1,371 1,119 991 861 817
Expense Example, with Redemption, 10 Years $ 2,657 $ 2,790 $ 2,790 $ 1,941 $ 2,972 $ 2,470 $ 2,209 $ 1,941 $ 1,846
[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] $ 216 $ 216
Expense Example, No Redemption, 3 Years [1] 780 780
Expense Example, No Redemption, 5 Years [1] 1,371 1,371
Expense Example, No Redemption, 10 Years [1] $ 2,790 $ 2,790
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
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 16 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - MFS 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): 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 0.09% 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) 0.88% 1.63% 1.63% 0.63% 1.63% 1.13% 0.88% 0.63% 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) 0.88% 1.63% 1.63% 0.63% 1.63% 1.13% 0.88% 0.63% 0.56%
Fee Waiver or Reimbursement over Assets, Date of Termination September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027 September 30, 2027
[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, 2027.
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 $ 660 $ 566 $ 266 $ 64 $ 166 $ 115 $ 90 $ 64 $ 57
Expense Example, with Redemption, 3 Years 840 814 514 202 514 359 281 202 182
Expense Example, with Redemption, 5 Years 1,035 1,087 887 351 887 622 488 351 317
Expense Example, with Redemption, 10 Years $ 1,597 $ 1,732 $ 1,732 $ 786 $ 1,933 $ 1,375 $ 1,084 $ 786 $ 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] $ 166 $ 166
Expense Example, No Redemption, 3 Years [1] 514 514
Expense Example, No Redemption, 5 Years [1] 887 887
Expense Example, No Redemption, 10 Years [1] $ 1,732 $ 1,732
[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 4% of the average value of its portfolio.
Portfolio Turnover, Rate 4.00%
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.