v3.26.1
Fees and Expenses - Prospectus Summary
Mar. 31, 2026
USD ($)
MFS Alabama Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Alabama Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Alabama Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.41% 0.41% 0.41% 0.35%
Expenses (as a percentage of Assets) 1.11% 1.86% 0.86% 0.80%
Fee Waiver or Reimbursement [1] (0.20%) (0.20%) (0.20%) (0.20%)
Net Expenses (as a percentage of Assets) 0.91% 1.66% 0.66% 0.60%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.90% of the class' average daily net assets annually for Class A shares, 1.65% of the class' average daily net assets annually for Class B shares, 0.65% of the class' average daily net assets annually for Class I shares, and 0.59% 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 July 31, 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 - Prospectus Summary - MFS Alabama Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 514 $ 569 $ 67 $ 61
Expense Example, with Redemption, 3 Years 744 865 254 235
Expense Example, with Redemption, 5 Years 992 1,187 457 425
Expense Example, with Redemption, 10 Years $ 1,702 $ 1,967 $ 1,042 $ 971
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - Prospectus Summary - MFS Alabama Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 169
Expense Example, No Redemption, 3 Years 565
Expense Example, No Redemption, 5 Years 987
Expense Example, No Redemption, 10 Years $ 1,967
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 14% of the average value of its portfolio.

Portfolio Turnover, Rate 14.00%
MFS Alabama Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Arkansas Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Arkansas Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Arkansas Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.26% 0.26% 0.26% 0.19%
Expenses (as a percentage of Assets) 0.96% 1.71% 0.71% 0.64%
Fee Waiver or Reimbursement [1] (0.26%) (0.26%) (0.11%) (0.11%)
Net Expenses (as a percentage of Assets) 0.70% 1.45% 0.60% 0.53%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 2027. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class A and Class B service fee to 0.10% of each class' average daily net assets annually until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 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 0.70% of the class' average daily net assets annually for Class A shares, 1.45% of the class' average daily net assets annually for Class B shares, 0.60% of the class' average daily net assets annually for Class I shares, and 0.53% 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 July 31, 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 - Prospectus Summary - MFS Arkansas Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 493 $ 548 $ 61 $ 54
Expense Example, with Redemption, 3 Years 693 813 216 194
Expense Example, with Redemption, 5 Years 909 1,104 384 346
Expense Example, with Redemption, 10 Years $ 1,530 $ 1,798 $ 872 $ 788
[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 - Prospectus Summary - MFS Arkansas Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 148
Expense Example, No Redemption, 3 Years 513
Expense Example, No Redemption, 5 Years 904
Expense Example, No Redemption, 10 Years $ 1,798
[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 12% of the average value of its portfolio.

Portfolio Turnover, Rate 12.00%
MFS Arkansas Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS California Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 12 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS California Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS California Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.15% 0.15% 0.15% 0.15% 0.08%
Expenses (as a percentage of Assets) 0.85% 1.60% 1.60% 0.60% 0.53%
Fee Waiver or Reimbursement [1] (0.19%) (0.19%) (0.04%) (0.04%) (0.03%)
Net Expenses (as a percentage of Assets) 0.66% 1.41% 1.56% 0.56% 0.50%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 2027. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class A and Class B service fee to 0.10% of each class' average daily net assets annually until modified by the fund’s Board of Trustees, but such agreement will continue until at least July 31, 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 0.65% of the class' average daily net assets annually for Class A shares, 1.40% of the class' average daily net assets annually for Class B shares, 1.55% of the class’ average daily net assets annually for Class C shares, 0.55% of the class' average daily net assets annually for Class I shares, and 0.49% 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 July 31, 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 - Prospectus Summary - MFS California Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class C
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 490 $ 544 $ 259 $ 57 $ 51
Expense Example, with Redemption, 3 Years 667 786 501 188 167
Expense Example, with Redemption, 5 Years 858 1,053 867 331 293
Expense Example, with Redemption, 10 Years $ 1,413 $ 1,683 $ 1,696 $ 746 $ 662
[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 - Prospectus Summary - MFS California Municipal Bond Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 144 $ 159
Expense Example, No Redemption, 3 Years [1] 486 501
Expense Example, No Redemption, 5 Years [1] 853 867
Expense Example, No Redemption, 10 Years [1] $ 1,683 $ 1,696
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate 15.00%
MFS California Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Georgia Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Georgia Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Georgia Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.29% 0.29% 0.29% 0.23%
Expenses (as a percentage of Assets) 0.99% 1.74% 0.74% 0.68%
Fee Waiver or Reimbursement [1] (0.09%) (0.09%) (0.09%) (0.08%)
Net Expenses (as a percentage of Assets) 0.90% 1.65% 0.65% 0.60%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.90% of the class' average daily net assets annually for Class A shares, 1.65% of the class' average daily net assets annually for Class B shares, 0.65% of the class' average daily net assets annually for Class I shares, and 0.60% 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 July 31, 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 - Prospectus Summary - MFS Georgia Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 513 $ 568 $ 66 $ 61
Expense Example, with Redemption, 3 Years 718 839 228 210
Expense Example, with Redemption, 5 Years 940 1,135 403 371
Expense Example, with Redemption, 10 Years $ 1,579 $ 1,846 $ 910 $ 839
[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 - Prospectus Summary - MFS Georgia Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 168
Expense Example, No Redemption, 3 Years 539
Expense Example, No Redemption, 5 Years 935
Expense Example, No Redemption, 10 Years $ 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.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 13% of the average value of its portfolio.

Portfolio Turnover, Rate 13.00%
MFS Georgia Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Maryland Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Maryland Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Maryland Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.30% 0.30% 0.30% 0.23%
Expenses (as a percentage of Assets) 1.00% 1.75% 0.75% 0.68%
Fee Waiver or Reimbursement [1] (0.14%) (0.14%) (0.14%) (0.12%)
Net Expenses (as a percentage of Assets) 0.86% 1.61% 0.61% 0.56%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.83% of the class' average daily net assets annually for Class A shares, 1.58% of the class' average daily net assets annually for Class B shares, 0.58% of the class' average daily net assets annually for Class I shares, and 0.53% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.03% 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 July 31, 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 - Prospectus Summary - MFS Maryland Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 509 $ 564 $ 62 $ 57
Expense Example, with Redemption, 3 Years 717 837 226 205
Expense Example, with Redemption, 5 Years 941 1,136 403 367
Expense Example, with Redemption, 10 Years $ 1,585 $ 1,852 $ 917 $ 835
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - Prospectus Summary - MFS Maryland Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 164
Expense Example, No Redemption, 3 Years 537
Expense Example, No Redemption, 5 Years 936
Expense Example, No Redemption, 10 Years $ 1,852
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 9% of the average value of its portfolio.

Portfolio Turnover, Rate 9.00%
MFS Maryland Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Massachusetts Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Massachusetts Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Massachusetts Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.18% 0.18% 0.18% 0.10%
Expenses (as a percentage of Assets) 0.88% 1.63% 0.63% 0.55%
Fee Waiver or Reimbursement [1] (0.06%) (0.06%) (0.06%) (0.05%)
Net Expenses (as a percentage of Assets) 0.82% 1.57% 0.57% 0.50%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.82% of the class' average daily net assets annually for Class A shares, 1.57% of the class' average daily net assets annually for Class B shares, 0.57% of the class' average daily net assets annually for Class I shares, and 0.50% 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 July 31, 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 - Prospectus Summary - MFS Massachusetts Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 505 $ 560 $ 58 $ 51
Expense Example, with Redemption, 3 Years 688 808 196 171
Expense Example, with Redemption, 5 Years 886 1,081 345 302
Expense Example, with Redemption, 10 Years $ 1,458 $ 1,727 $ 781 $ 684
[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 - Prospectus Summary - MFS Massachusetts Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 160
Expense Example, No Redemption, 3 Years 508
Expense Example, No Redemption, 5 Years 881
Expense Example, No Redemption, 10 Years $ 1,727
[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 12% of the average value of its portfolio.

Portfolio Turnover, Rate 12.00%
MFS Massachusetts Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Mississippi Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Mississippi Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Mississippi Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.43% 0.43% 0.43% 0.37%
Expenses (as a percentage of Assets) 1.13% 1.88% 0.88% 0.82%
Fee Waiver or Reimbursement [1] (0.37%) (0.47%) (0.22%) (0.22%)
Net Expenses (as a percentage of Assets) 0.76% 1.41% 0.66% 0.60%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 2027. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class A service fee to 0.10% of the class' average daily net assets annually until modified by the fund’s Board of Trustees, but such agreement will continue until at least July 31, 2027. MFD has agreed in writing to waive the Class B service fee to 0.00% of the class' average daily net assets annually until modified by the fund’s Board of Trustees, but such agreement will continue until at least July 31, 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 0.76% of the class' average daily net assets annually for Class A shares, 1.41% of the class' average daily net assets annually for Class B shares, 0.66% of the class' average daily net assets annually for Class I shares, and 0.60% 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 July 31, 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 - Prospectus Summary - MFS Mississippi Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 499 $ 544 $ 67 $ 61
Expense Example, with Redemption, 3 Years 734 845 259 240
Expense Example, with Redemption, 5 Years 987 1,172 466 433
Expense Example, with Redemption, 10 Years $ 1,710 $ 1,966 $ 1,064 $ 993
[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 - Prospectus Summary - MFS Mississippi Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 144
Expense Example, No Redemption, 3 Years 545
Expense Example, No Redemption, 5 Years 972
Expense Example, No Redemption, 10 Years $ 1,966
[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 7% of the average value of its portfolio.

Portfolio Turnover, Rate 7.00%
MFS Mississippi Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Municipal Income Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Municipal Income Fund
Class A
Class B
Class C
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS Municipal Income Fund
Class A
Class B
Class C
Class I
Class R6
Management Fees (as a percentage of Assets) 0.36% 0.36% 0.36% 0.36% 0.36%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.19% 0.19% 0.19% 0.19% 0.12%
Expenses (as a percentage of Assets) 0.80% 1.55% 1.55% 0.55% 0.48%
Fee Waiver or Reimbursement [1] (0.01%) (0.01%) (0.01%) (0.01%) (0.01%)
Net Expenses (as a percentage of Assets) 0.79% 1.54% 1.54% 0.54% 0.47%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.73% of the class' average daily net assets annually for Class A shares, 1.48% of the class' average daily net assets annually for each of Class B and Class C shares, 0.48% of the class' average daily net assets annually for Class I shares, and 0.42% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.08% of interest and/or investment-related expenses incurred in connection with the fund's investment activity which are excluded from the expense limitation described above.) This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 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 - Prospectus Summary - MFS Municipal Income Fund - USD ($)
Class A
Class B
[1]
Class C
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 502 $ 557 $ 257 $ 55 $ 48
Expense Example, with Redemption, 3 Years 669 789 489 175 153
Expense Example, with Redemption, 5 Years 849 1,044 844 306 268
Expense Example, with Redemption, 10 Years $ 1,372 $ 1,643 $ 1,643 $ 688 $ 603
[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 - Prospectus Summary - MFS Municipal Income Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 157 $ 157
Expense Example, No Redemption, 3 Years [1] 489 489
Expense Example, No Redemption, 5 Years [1] 844 844
Expense Example, No Redemption, 10 Years [1] $ 1,643 $ 1,643
[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 12% of the average value of its portfolio.

Portfolio Turnover, Rate 12.00%
MFS Municipal Income Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Municipal Income Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in "Sales Charges and Waivers and Reductions" on page 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 you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Municipal Income Fund
Class A1
Class B1
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00%
[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 - Prospectus Summary - MFS Municipal Income Fund
Class A1
Class B1
Management Fees (as a percentage of Assets) 0.36% 0.36%
Distribution and Service (12b-1) Fees 0.00% 1.00%
Other Expenses (as a percentage of Assets): 0.19% 0.19%
Expenses (as a percentage of Assets) 0.55% 1.55%
Fee Waiver or Reimbursement [1] (0.01%) (0.26%)
Net Expenses (as a percentage of Assets) 0.54% 1.29%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 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 July 31, 2027. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class B1 service fee to 0.00% of the class' average daily net assets annually until modified by the fund’s Board of Trustees, but such agreement will continue until at least July 31, 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 0.48% of the class' average daily net assets annually for Class A1 shares and 1.23% of the class' average daily net assets annually for Class B1 shares. ("Other Expenses" include 0.08% of interest and/or investment-related expenses incurred in connection with the fund's investment activity which are excluded from the expense limitation described above.) This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 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 - Prospectus Summary - MFS Municipal Income Fund - USD ($)
Class A1
Class B1
[1]
Expense Example, with Redemption, 1 Year $ 478 $ 531
Expense Example, with Redemption, 3 Years 593 764
Expense Example, with Redemption, 5 Years 718 1,020
Expense Example, with Redemption, 10 Years $ 1,084 $ 1,553
[1] Shares automatically convert to Class A1 shares approximately eight years after purchase; therefore, the expense examples reflect Class A1 share expenses after eight years.
Expense Example, No Redemption [Table]
Expense Example, No Redemption - Prospectus Summary - MFS Municipal Income Fund
Class B1
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 131
Expense Example, No Redemption, 3 Years 464
Expense Example, No Redemption, 5 Years 820
Expense Example, No Redemption, 10 Years $ 1,553
[1] Shares automatically convert to Class A1 shares approximately eight years after purchase; therefore, the expense examples reflect Class A1 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 12% of the average value of its portfolio.

Portfolio Turnover, Rate 12.00%
MFS Municipal Income Fund | Class A1  
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 Municipal Intermediate Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Municipal Intermediate Fund
A
C
I
R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS Municipal Intermediate Fund
A
C
I
R6
Management Fees (as a percentage of Assets) 0.35% 0.35% 0.35% 0.35%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.19% 0.19% 0.19% 0.12%
Expenses (as a percentage of Assets) 0.79% 1.54% 0.54% 0.47%
Fee Waiver or Reimbursement [1] (0.09%) (0.09%) (0.09%) (0.09%)
Net Expenses (as a percentage of Assets) 0.70% 1.45% 0.45% 0.38%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.70% of the class' average daily net assets annually for Class A shares, 1.45% of the class' average daily net assets annually for Class C shares, 0.45% of the class' average daily net assets annually for Class I shares, and 0.38% 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 July 31, 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 - Prospectus Summary - MFS Municipal Intermediate Fund - USD ($)
A
C
[1]
I
R6
Expense Example, with Redemption, 1 Year $ 493 $ 248 $ 46 $ 39
Expense Example, with Redemption, 3 Years 658 478 164 142
Expense Example, with Redemption, 5 Years 837 831 293 254
Expense Example, with Redemption, 10 Years $ 1,353 $ 1,624 $ 668 $ 583
[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 - Prospectus Summary - MFS Municipal Intermediate Fund
C
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 148
Expense Example, No Redemption, 3 Years 478
Expense Example, No Redemption, 5 Years 831
Expense Example, No Redemption, 10 Years $ 1,624
[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 10% of the average value of its portfolio.

Portfolio Turnover, Rate 10.00%
MFS Municipal Intermediate Fund | 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 New York Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 12 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS New York Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS New York Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.26% 0.26% 0.26% 0.26% 0.18%
Expenses (as a percentage of Assets) 0.96% 1.71% 1.71% 0.71% 0.63%
Fee Waiver or Reimbursement [1] (0.13%) (0.13%) (0.13%) (0.13%) (0.11%)
Net Expenses (as a percentage of Assets) 0.83% 1.58% 1.58% 0.58% 0.52%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.83% of the class' average daily net assets annually for Class A shares, 1.58% of the class' average daily net assets annually for each of Class B and Class C shares, 0.58% of the class' average daily net assets annually for Class I shares, and 0.52% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 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 - Prospectus Summary - MFS New York Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class C
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 506 $ 561 $ 261 $ 59 $ 53
Expense Example, with Redemption, 3 Years 705 826 526 214 191
Expense Example, with Redemption, 5 Years 921 1,116 916 382 340
Expense Example, with Redemption, 10 Years $ 1,542 $ 1,809 $ 1,809 $ 870 $ 776
[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 - Prospectus Summary - MFS New York Municipal Bond Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 161 $ 161
Expense Example, No Redemption, 3 Years [1] 526 526
Expense Example, No Redemption, 5 Years [1] 916 916
Expense Example, No Redemption, 10 Years [1] $ 1,809 $ 1,809
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 15% of the average value of its portfolio.

Portfolio Turnover, Rate 15.00%
MFS New York Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS North Carolina Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 12 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS North Carolina Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS North Carolina Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.16% 0.16% 0.16% 0.16% 0.08%
Expenses (as a percentage of Assets) 0.86% 1.61% 1.61% 0.61% 0.53%
Fee Waiver or Reimbursement [1] (0.02%) (0.02%) (0.02%) (0.02%) (0.01%)
Net Expenses (as a percentage of Assets) 0.84% 1.59% 1.59% 0.59% 0.52%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 Class A shares, 1.59% of the class' average daily net assets annually for each of Class B and Class C shares, 0.59% of the class' average daily net assets annually for Class I shares, and 0.52% of the class' average daily net assets annually for Class R6 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least July 31, 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 - Prospectus Summary - MFS North Carolina Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class C
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 507 $ 562 $ 262 $ 60 $ 53
Expense Example, with Redemption, 3 Years 686 806 506 193 169
Expense Example, with Redemption, 5 Years 880 1,074 874 338 295
Expense Example, with Redemption, 10 Years $ 1,439 $ 1,708 $ 1,708 $ 760 $ 664
[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 - Prospectus Summary - MFS North Carolina Municipal Bond Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 162 $ 162
Expense Example, No Redemption, 3 Years [1] 506 506
Expense Example, No Redemption, 5 Years [1] 874 874
Expense Example, No Redemption, 10 Years [1] $ 1,708 $ 1,708
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 20% of the average value of its portfolio.

Portfolio Turnover, Rate 20.00%
MFS North Carolina Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Pennsylvania Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Pennsylvania Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS Pennsylvania Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.26% 0.26% 0.26% 0.19%
Expenses (as a percentage of Assets) 0.96% 1.71% 0.71% 0.64%
Fee Waiver or Reimbursement [1] (0.25%) (0.25%) (0.10%) (0.10%)
Net Expenses (as a percentage of Assets) 0.71% 1.46% 0.61% 0.54%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 2027. MFS Fund Distributors, Inc. (MFD), has agreed in writing to waive the Class A and Class B service fee to 0.10% of each class' average daily net assets annually until modified by the fund’s Board of Trustees, but such agreement will continue until at least July 31, 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 0.69% of the class' average daily net assets annually for Class A shares, 1.44% of the class' average daily net assets annually for Class B shares, 0.59% of the class' average daily net assets annually for Class I shares, and 0.52% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.02% 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 July 31, 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 - Prospectus Summary - MFS Pennsylvania Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 494 $ 549 $ 62 $ 55
Expense Example, with Redemption, 3 Years 694 814 217 195
Expense Example, with Redemption, 5 Years 910 1,105 385 347
Expense Example, with Redemption, 10 Years $ 1,531 $ 1,799 $ 873 $ 789
[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 - Prospectus Summary - MFS Pennsylvania Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 149
Expense Example, No Redemption, 3 Years 514
Expense Example, No Redemption, 5 Years 905
Expense Example, No Redemption, 10 Years $ 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 8% of the average value of its portfolio.

Portfolio Turnover, Rate 8.00%
MFS Pennsylvania Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS South Carolina Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS South Carolina Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS South Carolina Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.22% 0.22% 0.22% 0.15%
Expenses (as a percentage of Assets) 0.92% 1.67% 0.67% 0.60%
Fee Waiver or Reimbursement [1] (0.06%) (0.06%) (0.06%) (0.05%)
Net Expenses (as a percentage of Assets) 0.86% 1.61% 0.61% 0.55%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 Class A shares, 1.59% of the class' average daily net assets annually for Class B shares, 0.59% of the class' average daily net assets annually for Class I shares, and 0.53% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.02% 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 July 31, 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 - Prospectus Summary - MFS South Carolina Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 509 $ 564 $ 62 $ 56
Expense Example, with Redemption, 3 Years 700 821 208 187
Expense Example, with Redemption, 5 Years 907 1,102 367 330
Expense Example, with Redemption, 10 Years $ 1,503 $ 1,771 $ 829 $ 745
[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 - Prospectus Summary - MFS South Carolina Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 164
Expense Example, No Redemption, 3 Years 521
Expense Example, No Redemption, 5 Years 902
Expense Example, No Redemption, 10 Years $ 1,771
[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 South Carolina Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS Virginia Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 12 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus.

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS Virginia Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 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%
[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 - Prospectus Summary - MFS Virginia Municipal Bond Fund
Class A
Class B
Class C
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.21% 0.21% 0.21% 0.21% 0.13%
Expenses (as a percentage of Assets) 0.91% 1.66% 1.66% 0.66% 0.58%
Fee Waiver or Reimbursement [1] (0.08%) (0.08%) (0.08%) (0.08%) (0.07%)
Net Expenses (as a percentage of Assets) 0.83% 1.58% 1.58% 0.58% 0.51%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.81% of the class' average daily net assets annually for Class A shares, 1.56% of the class' average daily net assets annually for each of Class B and Class C shares, 0.56% of the class' average daily net assets annually for Class I shares, and 0.49% of the class' average daily net assets annually for Class R6 shares. ("Other Expenses" include 0.02% 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 July 31, 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 - Prospectus Summary - MFS Virginia Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class C
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 506 $ 561 $ 261 $ 59 $ 52
Expense Example, with Redemption, 3 Years 695 816 516 203 179
Expense Example, with Redemption, 5 Years 900 1,095 895 360 317
Expense Example, with Redemption, 10 Years $ 1,490 $ 1,759 $ 1,759 $ 815 $ 719
[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 - Prospectus Summary - MFS Virginia Municipal Bond Fund - USD ($)
Class B
Class C
Expense Example, No Redemption, 1 Year [1] $ 161 $ 161
Expense Example, No Redemption, 3 Years [1] 516 516
Expense Example, No Redemption, 5 Years [1] 895 895
Expense Example, No Redemption, 10 Years [1] $ 1,759 $ 1,759
[1] Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.
Portfolio Turnover [Heading] Portfolio Turnover
Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 9% of the average value of its portfolio.

Portfolio Turnover, Rate 9.00%
MFS Virginia Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.
MFS West Virginia Municipal Bond Fund  
Prospectus [Line Items]  
Expense Heading [Optional Text] Fees and Expenses
Expense Narrative [Text Block]

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

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

Expense Breakpoint Discounts [Text] You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $100,000 in MFS funds.
Expense Breakpoint, Minimum Investment Required [Amount] $ 100,000
Shareholder Fees Caption [Optional Text] Shareholder Fees (fees paid directly from your investment):
Shareholder Fees [Table]
Shareholder Fees - Prospectus Summary - MFS West Virginia Municipal Bond Fund
Class A
Class B
Class I
Class R6
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.25% 0.00% 0.00% 0.00%
Maximum Deferred Sales Charge (as a percentage of Offering Price) 1.00% [1] 4.00% 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 - Prospectus Summary - MFS West Virginia Municipal Bond Fund
Class A
Class B
Class I
Class R6
Management Fees (as a percentage of Assets) 0.45% 0.45% 0.45% 0.45%
Distribution and Service (12b-1) Fees 0.25% 1.00% 0.00% 0.00%
Other Expenses (as a percentage of Assets): 0.35% 0.35% 0.35% 0.28%
Expenses (as a percentage of Assets) 1.05% 1.80% 0.80% 0.73%
Fee Waiver or Reimbursement [1] (0.18%) (0.18%) (0.18%) (0.18%)
Net Expenses (as a percentage of Assets) 0.87% 1.62% 0.62% 0.55%
Fee Waiver or Reimbursement over Assets, Date of Termination July 31, 2027 July 31, 2027 July 31, 2027 July 31, 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 July 31, 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 0.87% of the class' average daily net assets annually for Class A shares, 1.62% of the class' average daily net assets annually for Class B shares, 0.62% of the class' average daily net assets annually for Class I shares, and 0.55% 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 July 31, 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 - Prospectus Summary - MFS West Virginia Municipal Bond Fund - USD ($)
Class A
Class B
[1]
Class I
Class R6
Expense Example, with Redemption, 1 Year $ 510 $ 565 $ 63 $ 56
Expense Example, with Redemption, 3 Years 728 849 237 215
Expense Example, with Redemption, 5 Years 963 1,158 426 388
Expense Example, with Redemption, 10 Years $ 1,638 $ 1,904 $ 973 $ 890
[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 - Prospectus Summary - MFS West Virginia Municipal Bond Fund
Class B
USD ($)
[1]
Expense Example, No Redemption, 1 Year $ 165
Expense Example, No Redemption, 3 Years 549
Expense Example, No Redemption, 5 Years 958
Expense Example, No Redemption, 10 Years $ 1,904
[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 12% of the average value of its portfolio.

Portfolio Turnover, Rate 12.00%
MFS West Virginia Municipal Bond Fund | Class A  
Prospectus [Line Items]  
Expenses Deferred Charges [Text Block] This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.