| Form N-CSR Cover | 6 Months Ended |
| Sep. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | MFS MUNICIPAL SERIES TRUST |
| Entity Central Index Key | 0000751656 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Sep. 30, 2024 |
| Shareholder Report | 6 Months Ended |
| Sep. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | MFS MUNICIPAL SERIES TRUST |
| Entity Central Index Key | 0000751656 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Sep. 30, 2024 |
| C000006957 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Alabama Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFALX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.90 % |
| Expenses Paid, Amount | $ 46 |
| Expense Ratio, Percent | 0.90% |
| Net Assets | $ 73,469,555 |
| Holdings Count | Holding | 175 |
| Investment Company Portfolio Turnover | 12% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 73,469,555 Average Effective Maturity (yrs): 18.5 Total Number of Holdings: 175 Average Effective Duration (yrs): 7.8 Portfolio Turnover Rate (%): 12 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 14.1 % Universities - Colleges 12.2 % General Obligations - General Purpose 11.8 % Tax - Other 11.0 % Sales & Excise Tax Revenue 9.6 % Healthcare Revenue - Hospitals 7.8 % State & Local Agencies 5.6 % Utilities - Other 4.3 % Single Family Housing - State 4.3 % General Obligations - Schools 3.8 % Other Industries 15.5 % Composition including fixed income credit quality AAA 5.3 % AA 36.4 % A 36.0 % BBB 11.6 % BB 1.2 % CC 0.1 % Not Rated 6.8 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006958 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Alabama Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBABX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.65 % |
| Expenses Paid, Amount | $ 84 |
| Expense Ratio, Percent | 1.65% |
| Net Assets | $ 73,469,555 |
| Holdings Count | Holding | 175 |
| Investment Company Portfolio Turnover | 12% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 73,469,555 Average Effective Maturity (yrs): 18.5 Total Number of Holdings: 175 Average Effective Duration (yrs): 7.8 Portfolio Turnover Rate (%): 12 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 14.1 % Universities - Colleges 12.2 % General Obligations - General Purpose 11.8 % Tax - Other 11.0 % Sales & Excise Tax Revenue 9.6 % Healthcare Revenue - Hospitals 7.8 % State & Local Agencies 5.6 % Utilities - Other 4.3 % Single Family Housing - State 4.3 % General Obligations - Schools 3.8 % Other Industries 15.5 % Composition including fixed income credit quality AAA 5.3 % AA 36.4 % A 36.0 % BBB 11.6 % BB 1.2 % CC 0.1 % Not Rated 6.8 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169758 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Alabama Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MLALX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.65 % |
| Expenses Paid, Amount | $ 33 |
| Expense Ratio, Percent | 0.65% |
| Net Assets | $ 73,469,555 |
| Holdings Count | Holding | 175 |
| Investment Company Portfolio Turnover | 12% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 73,469,555 Average Effective Maturity (yrs): 18.5 Total Number of Holdings: 175 Average Effective Duration (yrs): 7.8 Portfolio Turnover Rate (%): 12 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 14.1 % Universities - Colleges 12.2 % General Obligations - General Purpose 11.8 % Tax - Other 11.0 % Sales & Excise Tax Revenue 9.6 % Healthcare Revenue - Hospitals 7.8 % State & Local Agencies 5.6 % Utilities - Other 4.3 % Single Family Housing - State 4.3 % General Obligations - Schools 3.8 % Other Industries 15.5 % Composition including fixed income credit quality AAA 5.3 % AA 36.4 % A 36.0 % BBB 11.6 % BB 1.2 % CC 0.1 % Not Rated 6.8 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194226 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Alabama Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPOLX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.59 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.59% |
| Net Assets | $ 73,469,555 |
| Holdings Count | Holding | 175 |
| Investment Company Portfolio Turnover | 12% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 73,469,555 Average Effective Maturity (yrs): 18.5 Total Number of Holdings: 175 Average Effective Duration (yrs): 7.8 Portfolio Turnover Rate (%): 12 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 14.1 % Universities - Colleges 12.2 % General Obligations - General Purpose 11.8 % Tax - Other 11.0 % Sales & Excise Tax Revenue 9.6 % Healthcare Revenue - Hospitals 7.8 % State & Local Agencies 5.6 % Utilities - Other 4.3 % Single Family Housing - State 4.3 % General Obligations - Schools 3.8 % Other Industries 15.5 % Composition including fixed income credit quality AAA 5.3 % AA 36.4 % A 36.0 % BBB 11.6 % BB 1.2 % CC 0.1 % Not Rated 6.8 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006959 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® New York Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MSNYX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.83 % |
| Expenses Paid, Amount | $ 42 |
| Expense Ratio, Percent | 0.83% |
| Net Assets | $ 180,674,852 |
| Holdings Count | Holding | 194 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 180,674,852 Average Effective Maturity (yrs): 19.7 Total Number of Holdings: 194 Average Effective Duration (yrs): 7.6 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.1 % Money Market Funds 3.9 % Industries Multi-Family Housing Revenue 16.6 % Healthcare Revenue - Hospitals 10.8 % Transportation - Special Tax 8.6 % Airport Revenue 7.0 % Secondary Schools 5.9 % Industrial Revenue - Airlines 5.7 % Tax - Other 5.5 % Miscellaneous Revenue - Other 5.5 % General Obligations - General Purpose 5.3 % Universities - Colleges 5.2 % Other Industries 23.9 % Composition including fixed income credit quality AAA 7.1 % AA 29.3 % A 20.3 % BBB 23.6 % BB 3.6 % B 1.2 % CCC 0.7 % CC 0.7 % Not Rated 9.6 % Money Market Funds 3.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006960 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® New York Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBNYX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.58 % |
| Expenses Paid, Amount | $ 81 |
| Expense Ratio, Percent | 1.58% |
| Net Assets | $ 180,674,852 |
| Holdings Count | Holding | 194 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 180,674,852 Average Effective Maturity (yrs): 19.7 Total Number of Holdings: 194 Average Effective Duration (yrs): 7.6 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.1 % Money Market Funds 3.9 % Industries Multi-Family Housing Revenue 16.6 % Healthcare Revenue - Hospitals 10.8 % Transportation - Special Tax 8.6 % Airport Revenue 7.0 % Secondary Schools 5.9 % Industrial Revenue - Airlines 5.7 % Tax - Other 5.5 % Miscellaneous Revenue - Other 5.5 % General Obligations - General Purpose 5.3 % Universities - Colleges 5.2 % Other Industries 23.9 % Composition including fixed income credit quality AAA 7.1 % AA 29.3 % A 20.3 % BBB 23.6 % BB 3.6 % B 1.2 % CCC 0.7 % CC 0.7 % Not Rated 9.6 % Money Market Funds 3.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006961 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® New York Municipal Bond Fund |
| Class Name | Class C |
| Trading Symbol | MCNYX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.58 % |
| Expenses Paid, Amount | $ 81 |
| Expense Ratio, Percent | 1.58% |
| Net Assets | $ 180,674,852 |
| Holdings Count | Holding | 194 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 180,674,852 Average Effective Maturity (yrs): 19.7 Total Number of Holdings: 194 Average Effective Duration (yrs): 7.6 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.1 % Money Market Funds 3.9 % Industries Multi-Family Housing Revenue 16.6 % Healthcare Revenue - Hospitals 10.8 % Transportation - Special Tax 8.6 % Airport Revenue 7.0 % Secondary Schools 5.9 % Industrial Revenue - Airlines 5.7 % Tax - Other 5.5 % Miscellaneous Revenue - Other 5.5 % General Obligations - General Purpose 5.3 % Universities - Colleges 5.2 % Other Industries 23.9 % Composition including fixed income credit quality AAA 7.1 % AA 29.3 % A 20.3 % BBB 23.6 % BB 3.6 % B 1.2 % CCC 0.7 % CC 0.7 % Not Rated 9.6 % Money Market Funds 3.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169759 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® New York Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MNYLX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.58 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.58% |
| Net Assets | $ 180,674,852 |
| Holdings Count | Holding | 194 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 180,674,852 Average Effective Maturity (yrs): 19.7 Total Number of Holdings: 194 Average Effective Duration (yrs): 7.6 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.1 % Money Market Funds 3.9 % Industries Multi-Family Housing Revenue 16.6 % Healthcare Revenue - Hospitals 10.8 % Transportation - Special Tax 8.6 % Airport Revenue 7.0 % Secondary Schools 5.9 % Industrial Revenue - Airlines 5.7 % Tax - Other 5.5 % Miscellaneous Revenue - Other 5.5 % General Obligations - General Purpose 5.3 % Universities - Colleges 5.2 % Other Industries 23.9 % Composition including fixed income credit quality AAA 7.1 % AA 29.3 % A 20.3 % BBB 23.6 % BB 3.6 % B 1.2 % CCC 0.7 % CC 0.7 % Not Rated 9.6 % Money Market Funds 3.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194228 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® New York Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPNYX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.50 % |
| Expenses Paid, Amount | $ 26 |
| Expense Ratio, Percent | 0.50% |
| Net Assets | $ 180,674,852 |
| Holdings Count | Holding | 194 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 180,674,852 Average Effective Maturity (yrs): 19.7 Total Number of Holdings: 194 Average Effective Duration (yrs): 7.6 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.1 % Money Market Funds 3.9 % Industries Multi-Family Housing Revenue 16.6 % Healthcare Revenue - Hospitals 10.8 % Transportation - Special Tax 8.6 % Airport Revenue 7.0 % Secondary Schools 5.9 % Industrial Revenue - Airlines 5.7 % Tax - Other 5.5 % Miscellaneous Revenue - Other 5.5 % General Obligations - General Purpose 5.3 % Universities - Colleges 5.2 % Other Industries 23.9 % Composition including fixed income credit quality AAA 7.1 % AA 29.3 % A 20.3 % BBB 23.6 % BB 3.6 % B 1.2 % CCC 0.7 % CC 0.7 % Not Rated 9.6 % Money Market Funds 3.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006962 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® North Carolina Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MSNCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.84 % |
| Expenses Paid, Amount | $ 43 |
| Expense Ratio, Percent | 0.84% |
| Net Assets | $ 467,031,208 |
| Holdings Count | Holding | 282 |
| Investment Company Portfolio Turnover | 8% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 467,031,208 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 282 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 8 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 12.2 % Single Family Housing - State 12.1 % Universities - Colleges 12.0 % Healthcare Revenue - Hospitals 11.9 % State & Local Agencies 10.7 % Healthcare Revenue - Long Term Care 8.0 % Airport Revenue 6.8 % Toll Roads 4.3 % Multi-Family Housing Revenue 4.2 % General Obligations - General Purpose 4.0 % Other Industries 13.8 % Composition including fixed income credit quality AAA 5.4 % AA 50.0 % A 19.2 % BBB 12.7 % BB 1.1 % B 0.5 % CCC 0.0 % Not Rated 8.5 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006963 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® North Carolina Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBNCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.59 % |
| Expenses Paid, Amount | $ 81 |
| Expense Ratio, Percent | 1.59% |
| Net Assets | $ 467,031,208 |
| Holdings Count | Holding | 282 |
| Investment Company Portfolio Turnover | 8% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 467,031,208 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 282 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 8 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 12.2 % Single Family Housing - State 12.1 % Universities - Colleges 12.0 % Healthcare Revenue - Hospitals 11.9 % State & Local Agencies 10.7 % Healthcare Revenue - Long Term Care 8.0 % Airport Revenue 6.8 % Toll Roads 4.3 % Multi-Family Housing Revenue 4.2 % General Obligations - General Purpose 4.0 % Other Industries 13.8 % Composition including fixed income credit quality AAA 5.4 % AA 50.0 % A 19.2 % BBB 12.7 % BB 1.1 % B 0.5 % CCC 0.0 % Not Rated 8.5 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006964 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® North Carolina Municipal Bond Fund |
| Class Name | Class C |
| Trading Symbol | MCNCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.59 % |
| Expenses Paid, Amount | $ 81 |
| Expense Ratio, Percent | 1.59% |
| Net Assets | $ 467,031,208 |
| Holdings Count | Holding | 282 |
| Investment Company Portfolio Turnover | 8% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 467,031,208 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 282 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 8 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 12.2 % Single Family Housing - State 12.1 % Universities - Colleges 12.0 % Healthcare Revenue - Hospitals 11.9 % State & Local Agencies 10.7 % Healthcare Revenue - Long Term Care 8.0 % Airport Revenue 6.8 % Toll Roads 4.3 % Multi-Family Housing Revenue 4.2 % General Obligations - General Purpose 4.0 % Other Industries 13.8 % Composition including fixed income credit quality AAA 5.4 % AA 50.0 % A 19.2 % BBB 12.7 % BB 1.1 % B 0.5 % CCC 0.0 % Not Rated 8.5 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169760 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® North Carolina Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MNCLX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.59 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.59% |
| Net Assets | $ 467,031,208 |
| Holdings Count | Holding | 282 |
| Investment Company Portfolio Turnover | 8% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 467,031,208 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 282 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 8 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 12.2 % Single Family Housing - State 12.1 % Universities - Colleges 12.0 % Healthcare Revenue - Hospitals 11.9 % State & Local Agencies 10.7 % Healthcare Revenue - Long Term Care 8.0 % Airport Revenue 6.8 % Toll Roads 4.3 % Multi-Family Housing Revenue 4.2 % General Obligations - General Purpose 4.0 % Other Industries 13.8 % Composition including fixed income credit quality AAA 5.4 % AA 50.0 % A 19.2 % BBB 12.7 % BB 1.1 % B 0.5 % CCC 0.0 % Not Rated 8.5 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194230 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® North Carolina Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPNCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.52 % |
| Expenses Paid, Amount | $ 27 |
| Expense Ratio, Percent | 0.52% |
| Net Assets | $ 467,031,208 |
| Holdings Count | Holding | 282 |
| Investment Company Portfolio Turnover | 8% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 467,031,208 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 282 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 8 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.4 % Money Market Funds 2.6 % Industries Water & Sewer Utility Revenue 12.2 % Single Family Housing - State 12.1 % Universities - Colleges 12.0 % Healthcare Revenue - Hospitals 11.9 % State & Local Agencies 10.7 % Healthcare Revenue - Long Term Care 8.0 % Airport Revenue 6.8 % Toll Roads 4.3 % Multi-Family Housing Revenue 4.2 % General Obligations - General Purpose 4.0 % Other Industries 13.8 % Composition including fixed income credit quality AAA 5.4 % AA 50.0 % A 19.2 % BBB 12.7 % BB 1.1 % B 0.5 % CCC 0.0 % Not Rated 8.5 % Money Market Funds 2.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006967 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® South Carolina Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFSCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.84 % |
| Expenses Paid, Amount | $ 43 |
| Expense Ratio, Percent | 0.84% |
| Net Assets | $ 223,866,223 |
| Holdings Count | Holding | 231 |
| Investment Company Portfolio Turnover | 10% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 223,866,223 Average Effective Maturity (yrs): 18.2 Total Number of Holdings: 231 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 10 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Water & Sewer Utility Revenue 13.6 % Healthcare Revenue - Hospitals 12.7 % Single Family Housing - State 10.9 % State & Local Agencies 7.7 % General Obligations - Schools 6.6 % Port Revenue 6.6 % Utilities - Municipal Owned 5.9 % Airport Revenue 5.3 % Universities - Colleges 5.1 % General Obligations - General Purpose 4.5 % Other Industries 21.1 % Composition including fixed income credit quality AAA 12.7 % AA 32.3 % A 37.6 % BBB 5.4 % BB 1.4 % B 0.0 % CC 0.0 % Not Rated 7.3 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006968 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® South Carolina Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBSCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.59 % |
| Expenses Paid, Amount | $ 81 |
| Expense Ratio, Percent | 1.59% |
| Net Assets | $ 223,866,223 |
| Holdings Count | Holding | 231 |
| Investment Company Portfolio Turnover | 10% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 223,866,223 Average Effective Maturity (yrs): 18.2 Total Number of Holdings: 231 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 10 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Water & Sewer Utility Revenue 13.6 % Healthcare Revenue - Hospitals 12.7 % Single Family Housing - State 10.9 % State & Local Agencies 7.7 % General Obligations - Schools 6.6 % Port Revenue 6.6 % Utilities - Municipal Owned 5.9 % Airport Revenue 5.3 % Universities - Colleges 5.1 % General Obligations - General Purpose 4.5 % Other Industries 21.1 % Composition including fixed income credit quality AAA 12.7 % AA 32.3 % A 37.6 % BBB 5.4 % BB 1.4 % B 0.0 % CC 0.0 % Not Rated 7.3 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169762 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® South Carolina Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MTSCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.59 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.59% |
| Net Assets | $ 223,866,223 |
| Holdings Count | Holding | 231 |
| Investment Company Portfolio Turnover | 10% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 223,866,223 Average Effective Maturity (yrs): 18.2 Total Number of Holdings: 231 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 10 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Water & Sewer Utility Revenue 13.6 % Healthcare Revenue - Hospitals 12.7 % Single Family Housing - State 10.9 % State & Local Agencies 7.7 % General Obligations - Schools 6.6 % Port Revenue 6.6 % Utilities - Municipal Owned 5.9 % Airport Revenue 5.3 % Universities - Colleges 5.1 % General Obligations - General Purpose 4.5 % Other Industries 21.1 % Composition including fixed income credit quality AAA 12.7 % AA 32.3 % A 37.6 % BBB 5.4 % BB 1.4 % B 0.0 % CC 0.0 % Not Rated 7.3 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194234 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® South Carolina Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPOCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.53 % |
| Expenses Paid, Amount | $ 27 |
| Expense Ratio, Percent | 0.53% |
| Net Assets | $ 223,866,223 |
| Holdings Count | Holding | 231 |
| Investment Company Portfolio Turnover | 10% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 223,866,223 Average Effective Maturity (yrs): 18.2 Total Number of Holdings: 231 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 10 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Water & Sewer Utility Revenue 13.6 % Healthcare Revenue - Hospitals 12.7 % Single Family Housing - State 10.9 % State & Local Agencies 7.7 % General Obligations - Schools 6.6 % Port Revenue 6.6 % Utilities - Municipal Owned 5.9 % Airport Revenue 5.3 % Universities - Colleges 5.1 % General Obligations - General Purpose 4.5 % Other Industries 21.1 % Composition including fixed income credit quality AAA 12.7 % AA 32.3 % A 37.6 % BBB 5.4 % BB 1.4 % B 0.0 % CC 0.0 % Not Rated 7.3 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006971 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Virginia Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MSVAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.81 % |
| Expenses Paid, Amount | $ 41 |
| Expense Ratio, Percent | 0.81% |
| Net Assets | $ 358,314,906 |
| Holdings Count | Holding | 254 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 358,314,906 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 254 Average Effective Duration (yrs): 6.9 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.1 % Money Market Funds 0.9 % Industries Multi-Family Housing Revenue 14.8 % Healthcare Revenue - Hospitals 13.6 % State & Local Agencies 9.0 % Water & Sewer Utility Revenue 8.6 % General Obligations - General Purpose 7.8 % Universities - Colleges 7.5 % Toll Roads 6.1 % Sales & Excise Tax Revenue 4.6 % Airport Revenue 4.5 % Transportation - Special Tax 4.3 % Other Industries 19.2 % Composition including fixed income credit quality AAA 17.5 % AA 46.1 % A 17.1 % BBB 8.6 % BB 1.5 % B 0.3 % CCC 0.6 % CC 0.1 % Not Rated 7.3 % Money Market Funds 0.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006972 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Virginia Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBVAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.56 % |
| Expenses Paid, Amount | $ 79 |
| Expense Ratio, Percent | 1.56% |
| Net Assets | $ 358,314,906 |
| Holdings Count | Holding | 254 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 358,314,906 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 254 Average Effective Duration (yrs): 6.9 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.1 % Money Market Funds 0.9 % Industries Multi-Family Housing Revenue 14.8 % Healthcare Revenue - Hospitals 13.6 % State & Local Agencies 9.0 % Water & Sewer Utility Revenue 8.6 % General Obligations - General Purpose 7.8 % Universities - Colleges 7.5 % Toll Roads 6.1 % Sales & Excise Tax Revenue 4.6 % Airport Revenue 4.5 % Transportation - Special Tax 4.3 % Other Industries 19.2 % Composition including fixed income credit quality AAA 17.5 % AA 46.1 % A 17.1 % BBB 8.6 % BB 1.5 % B 0.3 % CCC 0.6 % CC 0.1 % Not Rated 7.3 % Money Market Funds 0.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006973 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Virginia Municipal Bond Fund |
| Class Name | Class C |
| Trading Symbol | MVACX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.56 % |
| Expenses Paid, Amount | $ 79 |
| Expense Ratio, Percent | 1.56% |
| Net Assets | $ 358,314,906 |
| Holdings Count | Holding | 254 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 358,314,906 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 254 Average Effective Duration (yrs): 6.9 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.1 % Money Market Funds 0.9 % Industries Multi-Family Housing Revenue 14.8 % Healthcare Revenue - Hospitals 13.6 % State & Local Agencies 9.0 % Water & Sewer Utility Revenue 8.6 % General Obligations - General Purpose 7.8 % Universities - Colleges 7.5 % Toll Roads 6.1 % Sales & Excise Tax Revenue 4.6 % Airport Revenue 4.5 % Transportation - Special Tax 4.3 % Other Industries 19.2 % Composition including fixed income credit quality AAA 17.5 % AA 46.1 % A 17.1 % BBB 8.6 % BB 1.5 % B 0.3 % CCC 0.6 % CC 0.1 % Not Rated 7.3 % Money Market Funds 0.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169764 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Virginia Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MIVAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.56 % |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.56% |
| Net Assets | $ 358,314,906 |
| Holdings Count | Holding | 254 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 358,314,906 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 254 Average Effective Duration (yrs): 6.9 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.1 % Money Market Funds 0.9 % Industries Multi-Family Housing Revenue 14.8 % Healthcare Revenue - Hospitals 13.6 % State & Local Agencies 9.0 % Water & Sewer Utility Revenue 8.6 % General Obligations - General Purpose 7.8 % Universities - Colleges 7.5 % Toll Roads 6.1 % Sales & Excise Tax Revenue 4.6 % Airport Revenue 4.5 % Transportation - Special Tax 4.3 % Other Industries 19.2 % Composition including fixed income credit quality AAA 17.5 % AA 46.1 % A 17.1 % BBB 8.6 % BB 1.5 % B 0.3 % CCC 0.6 % CC 0.1 % Not Rated 7.3 % Money Market Funds 0.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194238 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Virginia Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPVOX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.48 % |
| Expenses Paid, Amount | $ 24 |
| Expense Ratio, Percent | 0.48% |
| Net Assets | $ 358,314,906 |
| Holdings Count | Holding | 254 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 358,314,906 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 254 Average Effective Duration (yrs): 6.9 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.1 % Money Market Funds 0.9 % Industries Multi-Family Housing Revenue 14.8 % Healthcare Revenue - Hospitals 13.6 % State & Local Agencies 9.0 % Water & Sewer Utility Revenue 8.6 % General Obligations - General Purpose 7.8 % Universities - Colleges 7.5 % Toll Roads 6.1 % Sales & Excise Tax Revenue 4.6 % Airport Revenue 4.5 % Transportation - Special Tax 4.3 % Other Industries 19.2 % Composition including fixed income credit quality AAA 17.5 % AA 46.1 % A 17.1 % BBB 8.6 % BB 1.5 % B 0.3 % CCC 0.6 % CC 0.1 % Not Rated 7.3 % Money Market Funds 0.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006974 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® West Virginia Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFWVX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.87 % |
| Expenses Paid, Amount | $ 44 |
| Expense Ratio, Percent | 0.87% |
| Net Assets | $ 97,299,607 |
| Holdings Count | Holding | 162 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 97,299,607 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 162 Average Effective Duration (yrs): 6.7 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.8 % Money Market Funds 3.2 % Industries Single Family Housing - State 14.4 % Healthcare Revenue - Hospitals 14.0 % Water & Sewer Utility Revenue 10.4 % State & Local Agencies 9.9 % Universities - Colleges 8.9 % Miscellaneous Revenue - Other 6.5 % General Obligations - General Purpose 6.4 % General Obligations - Schools 5.1 % Sales & Excise Tax Revenue 4.5 % Tax - Other 3.6 % Other Industries 16.3 % Composition including fixed income credit quality AAA 14.0 % AA 27.8 % A 34.9 % BBB 10.6 % BB 0.5 % B 0.0 % Not Rated 9.0 % Money Market Funds 3.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006975 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® West Virginia Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBWVX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.62 % |
| Expenses Paid, Amount | $ 82 |
| Expense Ratio, Percent | 1.62% |
| Net Assets | $ 97,299,607 |
| Holdings Count | Holding | 162 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 97,299,607 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 162 Average Effective Duration (yrs): 6.7 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.8 % Money Market Funds 3.2 % Industries Single Family Housing - State 14.4 % Healthcare Revenue - Hospitals 14.0 % Water & Sewer Utility Revenue 10.4 % State & Local Agencies 9.9 % Universities - Colleges 8.9 % Miscellaneous Revenue - Other 6.5 % General Obligations - General Purpose 6.4 % General Obligations - Schools 5.1 % Sales & Excise Tax Revenue 4.5 % Tax - Other 3.6 % Other Industries 16.3 % Composition including fixed income credit quality AAA 14.0 % AA 27.8 % A 34.9 % BBB 10.6 % BB 0.5 % B 0.0 % Not Rated 9.0 % Money Market Funds 3.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169765 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® West Virginia Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MWVIX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.62 % |
| Expenses Paid, Amount | $ 32 |
| Expense Ratio, Percent | 0.62% |
| Net Assets | $ 97,299,607 |
| Holdings Count | Holding | 162 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 97,299,607 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 162 Average Effective Duration (yrs): 6.7 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.8 % Money Market Funds 3.2 % Industries Single Family Housing - State 14.4 % Healthcare Revenue - Hospitals 14.0 % Water & Sewer Utility Revenue 10.4 % State & Local Agencies 9.9 % Universities - Colleges 8.9 % Miscellaneous Revenue - Other 6.5 % General Obligations - General Purpose 6.4 % General Obligations - Schools 5.1 % Sales & Excise Tax Revenue 4.5 % Tax - Other 3.6 % Other Industries 16.3 % Composition including fixed income credit quality AAA 14.0 % AA 27.8 % A 34.9 % BBB 10.6 % BB 0.5 % B 0.0 % Not Rated 9.0 % Money Market Funds 3.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194240 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® West Virginia Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPWVX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.54 % |
| Expenses Paid, Amount | $ 28 |
| Expense Ratio, Percent | 0.54% |
| Net Assets | $ 97,299,607 |
| Holdings Count | Holding | 162 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 97,299,607 Average Effective Maturity (yrs): 17.2 Total Number of Holdings: 162 Average Effective Duration (yrs): 6.7 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.8 % Money Market Funds 3.2 % Industries Single Family Housing - State 14.4 % Healthcare Revenue - Hospitals 14.0 % Water & Sewer Utility Revenue 10.4 % State & Local Agencies 9.9 % Universities - Colleges 8.9 % Miscellaneous Revenue - Other 6.5 % General Obligations - General Purpose 6.4 % General Obligations - Schools 5.1 % Sales & Excise Tax Revenue 4.5 % Tax - Other 3.6 % Other Industries 16.3 % Composition including fixed income credit quality AAA 14.0 % AA 27.8 % A 34.9 % BBB 10.6 % BB 0.5 % B 0.0 % Not Rated 9.0 % Money Market Funds 3.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006976 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Arkansas Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFARX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.70 % |
| Expenses Paid, Amount | $ 36 |
| Expense Ratio, Percent | 0.70% |
| Net Assets | $ 150,302,413 |
| Holdings Count | Holding | 204 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 150,302,413 Average Effective Maturity (yrs): 16.9 Total Number of Holdings: 204 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 98.8 % Money Market Funds 1.2 % Industries Sales & Excise Tax Revenue 20.5 % Universities - Colleges 13.2 % Water & Sewer Utility Revenue 13.0 % Healthcare Revenue - Hospitals 11.8 % General Obligations - Schools 11.2 % Miscellaneous Revenue - Other 4.5 % Tax - Other 4.2 % General Obligations - General Purpose 3.9 % Utilities - Other 3.9 % Single Family Housing - State 3.8 % Other Industries 10.0 % Composition including fixed income credit quality AA 57.5 % A 22.9 % BBB 9.9 % BB 0.8 % B 0.0 % Not Rated 7.7 % Money Market Funds 1.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006977 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Arkansas Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBARX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.45 % |
| Expenses Paid, Amount | $ 74 |
| Expense Ratio, Percent | 1.45% |
| Net Assets | $ 150,302,413 |
| Holdings Count | Holding | 204 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 150,302,413 Average Effective Maturity (yrs): 16.9 Total Number of Holdings: 204 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 98.8 % Money Market Funds 1.2 % Industries Sales & Excise Tax Revenue 20.5 % Universities - Colleges 13.2 % Water & Sewer Utility Revenue 13.0 % Healthcare Revenue - Hospitals 11.8 % General Obligations - Schools 11.2 % Miscellaneous Revenue - Other 4.5 % Tax - Other 4.2 % General Obligations - General Purpose 3.9 % Utilities - Other 3.9 % Single Family Housing - State 3.8 % Other Industries 10.0 % Composition including fixed income credit quality AA 57.5 % A 22.9 % BBB 9.9 % BB 0.8 % B 0.0 % Not Rated 7.7 % Money Market Funds 1.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169766 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Arkansas Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MARLX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.60 % |
| Expenses Paid, Amount | $ 31 |
| Expense Ratio, Percent | 0.60% |
| Net Assets | $ 150,302,413 |
| Holdings Count | Holding | 204 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 150,302,413 Average Effective Maturity (yrs): 16.9 Total Number of Holdings: 204 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 98.8 % Money Market Funds 1.2 % Industries Sales & Excise Tax Revenue 20.5 % Universities - Colleges 13.2 % Water & Sewer Utility Revenue 13.0 % Healthcare Revenue - Hospitals 11.8 % General Obligations - Schools 11.2 % Miscellaneous Revenue - Other 4.5 % Tax - Other 4.2 % General Obligations - General Purpose 3.9 % Utilities - Other 3.9 % Single Family Housing - State 3.8 % Other Industries 10.0 % Composition including fixed income credit quality AA 57.5 % A 22.9 % BBB 9.9 % BB 0.8 % B 0.0 % Not Rated 7.7 % Money Market Funds 1.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194242 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Arkansas Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPRAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.53 % |
| Expenses Paid, Amount | $ 27 |
| Expense Ratio, Percent | 0.53% |
| Net Assets | $ 150,302,413 |
| Holdings Count | Holding | 204 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 150,302,413 Average Effective Maturity (yrs): 16.9 Total Number of Holdings: 204 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 98.8 % Money Market Funds 1.2 % Industries Sales & Excise Tax Revenue 20.5 % Universities - Colleges 13.2 % Water & Sewer Utility Revenue 13.0 % Healthcare Revenue - Hospitals 11.8 % General Obligations - Schools 11.2 % Miscellaneous Revenue - Other 4.5 % Tax - Other 4.2 % General Obligations - General Purpose 3.9 % Utilities - Other 3.9 % Single Family Housing - State 3.8 % Other Industries 10.0 % Composition including fixed income credit quality AA 57.5 % A 22.9 % BBB 9.9 % BB 0.8 % B 0.0 % Not Rated 7.7 % Money Market Funds 1.2 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006978 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® California Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MCFTX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.67 % |
| Expenses Paid, Amount | $ 34 |
| Expense Ratio, Percent | 0.67% |
| Net Assets | $ 672,191,368 |
| Holdings Count | Holding | 403 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 672,191,368 Average Effective Maturity (yrs): 18.6 Total Number of Holdings: 403 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Multi-Family Housing Revenue 14.6 % General Obligations - Schools 14.0 % Healthcare Revenue - Hospitals 10.6 % Airport Revenue 9.5 % Tax Assessment 5.8 % Utilities - Other 5.0 % Secondary Schools 4.1 % State & Local Agencies 4.0 % Universities - Colleges 3.7 % Water & Sewer Utility Revenue 3.6 % Other Industries 25.1 % Composition including fixed income credit quality AAA 11.2 % AA 32.8 % A 24.1 % BBB 14.8 % BB 2.7 % B 0.3 % Not Rated 10.8 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006979 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® California Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBCAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.42 % |
| Expenses Paid, Amount | $ 72 |
| Expense Ratio, Percent | 1.42% |
| Net Assets | $ 672,191,368 |
| Holdings Count | Holding | 403 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 672,191,368 Average Effective Maturity (yrs): 18.6 Total Number of Holdings: 403 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Multi-Family Housing Revenue 14.6 % General Obligations - Schools 14.0 % Healthcare Revenue - Hospitals 10.6 % Airport Revenue 9.5 % Tax Assessment 5.8 % Utilities - Other 5.0 % Secondary Schools 4.1 % State & Local Agencies 4.0 % Universities - Colleges 3.7 % Water & Sewer Utility Revenue 3.6 % Other Industries 25.1 % Composition including fixed income credit quality AAA 11.2 % AA 32.8 % A 24.1 % BBB 14.8 % BB 2.7 % B 0.3 % Not Rated 10.8 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006980 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® California Municipal Bond Fund |
| Class Name | Class C |
| Trading Symbol | MCCAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.57 % |
| Expenses Paid, Amount | $ 80 |
| Expense Ratio, Percent | 1.57% |
| Net Assets | $ 672,191,368 |
| Holdings Count | Holding | 403 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 672,191,368 Average Effective Maturity (yrs): 18.6 Total Number of Holdings: 403 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Multi-Family Housing Revenue 14.6 % General Obligations - Schools 14.0 % Healthcare Revenue - Hospitals 10.6 % Airport Revenue 9.5 % Tax Assessment 5.8 % Utilities - Other 5.0 % Secondary Schools 4.1 % State & Local Agencies 4.0 % Universities - Colleges 3.7 % Water & Sewer Utility Revenue 3.6 % Other Industries 25.1 % Composition including fixed income credit quality AAA 11.2 % AA 32.8 % A 24.1 % BBB 14.8 % BB 2.7 % B 0.3 % Not Rated 10.8 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169767 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® California Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MCAVX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.57 % |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.57% |
| Net Assets | $ 672,191,368 |
| Holdings Count | Holding | 403 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 672,191,368 Average Effective Maturity (yrs): 18.6 Total Number of Holdings: 403 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Multi-Family Housing Revenue 14.6 % General Obligations - Schools 14.0 % Healthcare Revenue - Hospitals 10.6 % Airport Revenue 9.5 % Tax Assessment 5.8 % Utilities - Other 5.0 % Secondary Schools 4.1 % State & Local Agencies 4.0 % Universities - Colleges 3.7 % Water & Sewer Utility Revenue 3.6 % Other Industries 25.1 % Composition including fixed income credit quality AAA 11.2 % AA 32.8 % A 24.1 % BBB 14.8 % BB 2.7 % B 0.3 % Not Rated 10.8 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194244 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® California Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPOAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.51 % |
| Expenses Paid, Amount | $ 26 |
| Expense Ratio, Percent | 0.51% |
| Net Assets | $ 672,191,368 |
| Holdings Count | Holding | 403 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 672,191,368 Average Effective Maturity (yrs): 18.6 Total Number of Holdings: 403 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 4 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 96.7 % Money Market Funds 3.3 % Industries Multi-Family Housing Revenue 14.6 % General Obligations - Schools 14.0 % Healthcare Revenue - Hospitals 10.6 % Airport Revenue 9.5 % Tax Assessment 5.8 % Utilities - Other 5.0 % Secondary Schools 4.1 % State & Local Agencies 4.0 % Universities - Colleges 3.7 % Water & Sewer Utility Revenue 3.6 % Other Industries 25.1 % Composition including fixed income credit quality AAA 11.2 % AA 32.8 % A 24.1 % BBB 14.8 % BB 2.7 % B 0.3 % Not Rated 10.8 % Money Market Funds 3.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006983 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Georgia Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MMGAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.90 % |
| Expenses Paid, Amount | $ 46 |
| Expense Ratio, Percent | 0.90% |
| Net Assets | $ 114,301,746 |
| Holdings Count | Holding | 217 |
| Investment Company Portfolio Turnover | 6% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 114,301,746 Average Effective Maturity (yrs): 17.9 Total Number of Holdings: 217 Average Effective Duration (yrs): 7.4 Portfolio Turnover Rate (%): 6 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.7 % Money Market Funds 2.3 % Industries Universities - Colleges 14.6 % Healthcare Revenue - Hospitals 13.1 % Utilities - Municipal Owned 9.6 % Water & Sewer Utility Revenue 9.3 % Single Family Housing - State 6.9 % Miscellaneous Revenue - Other 6.4 % Multi-Family Housing Revenue 5.7 % Airport Revenue 5.7 % Sales & Excise Tax Revenue 5.4 % General Obligations - Schools 4.7 % Other Industries 18.6 % Composition including fixed income credit quality AAA 11.7 % AA 31.5 % A 37.7 % BBB 8.9 % BB 1.2 % B 0.0 % CC 0.1 % Not Rated 6.6 % Money Market Funds 2.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006984 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Georgia Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBGAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.65 % |
| Expenses Paid, Amount | $ 84 |
| Expense Ratio, Percent | 1.65% |
| Net Assets | $ 114,301,746 |
| Holdings Count | Holding | 217 |
| Investment Company Portfolio Turnover | 6% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 114,301,746 Average Effective Maturity (yrs): 17.9 Total Number of Holdings: 217 Average Effective Duration (yrs): 7.4 Portfolio Turnover Rate (%): 6 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.7 % Money Market Funds 2.3 % Industries Universities - Colleges 14.6 % Healthcare Revenue - Hospitals 13.1 % Utilities - Municipal Owned 9.6 % Water & Sewer Utility Revenue 9.3 % Single Family Housing - State 6.9 % Miscellaneous Revenue - Other 6.4 % Multi-Family Housing Revenue 5.7 % Airport Revenue 5.7 % Sales & Excise Tax Revenue 5.4 % General Obligations - Schools 4.7 % Other Industries 18.6 % Composition including fixed income credit quality AAA 11.7 % AA 31.5 % A 37.7 % BBB 8.9 % BB 1.2 % B 0.0 % CC 0.1 % Not Rated 6.6 % Money Market Funds 2.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169768 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Georgia Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MGATX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.65 % |
| Expenses Paid, Amount | $ 33 |
| Expense Ratio, Percent | 0.65% |
| Net Assets | $ 114,301,746 |
| Holdings Count | Holding | 217 |
| Investment Company Portfolio Turnover | 6% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 114,301,746 Average Effective Maturity (yrs): 17.9 Total Number of Holdings: 217 Average Effective Duration (yrs): 7.4 Portfolio Turnover Rate (%): 6 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.7 % Money Market Funds 2.3 % Industries Universities - Colleges 14.6 % Healthcare Revenue - Hospitals 13.1 % Utilities - Municipal Owned 9.6 % Water & Sewer Utility Revenue 9.3 % Single Family Housing - State 6.9 % Miscellaneous Revenue - Other 6.4 % Multi-Family Housing Revenue 5.7 % Airport Revenue 5.7 % Sales & Excise Tax Revenue 5.4 % General Obligations - Schools 4.7 % Other Industries 18.6 % Composition including fixed income credit quality AAA 11.7 % AA 31.5 % A 37.7 % BBB 8.9 % BB 1.2 % B 0.0 % CC 0.1 % Not Rated 6.6 % Money Market Funds 2.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194246 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Georgia Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPGOX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.60 % |
| Expenses Paid, Amount | $ 31 |
| Expense Ratio, Percent | 0.60% |
| Net Assets | $ 114,301,746 |
| Holdings Count | Holding | 217 |
| Investment Company Portfolio Turnover | 6% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 114,301,746 Average Effective Maturity (yrs): 17.9 Total Number of Holdings: 217 Average Effective Duration (yrs): 7.4 Portfolio Turnover Rate (%): 6 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.7 % Money Market Funds 2.3 % Industries Universities - Colleges 14.6 % Healthcare Revenue - Hospitals 13.1 % Utilities - Municipal Owned 9.6 % Water & Sewer Utility Revenue 9.3 % Single Family Housing - State 6.9 % Miscellaneous Revenue - Other 6.4 % Multi-Family Housing Revenue 5.7 % Airport Revenue 5.7 % Sales & Excise Tax Revenue 5.4 % General Obligations - Schools 4.7 % Other Industries 18.6 % Composition including fixed income credit quality AAA 11.7 % AA 31.5 % A 37.7 % BBB 8.9 % BB 1.2 % B 0.0 % CC 0.1 % Not Rated 6.6 % Money Market Funds 2.3 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006985 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Maryland Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFSMX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.83 % |
| Expenses Paid, Amount | $ 42 |
| Expense Ratio, Percent | 0.83% |
| Net Assets | $ 129,923,775 |
| Holdings Count | Holding | 215 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 129,923,775 Average Effective Maturity (yrs): 15.6 Total Number of Holdings: 215 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 3 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Healthcare Revenue - Hospitals 16.4 % State & Local Agencies 13.1 % General Obligations - General Purpose 12.0 % Single Family Housing - State 10.4 % Multi-Family Housing Revenue 9.5 % Transportation - Special Tax 5.0 % Universities - Colleges 4.1 % Tax Assessment 3.9 % Healthcare Revenue - Long Term Care 2.7 % Universities - Dormitories 2.6 % Other Industries 20.3 % Composition including fixed income credit quality AAA 13.6 % AA 33.8 % A 26.5 % BBB 12.6 % BB 0.9 % B 0.2 % CCC 0.1 % Not Rated 9.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006986 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Maryland Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBMDX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.58 % |
| Expenses Paid, Amount | $ 80 |
| Expense Ratio, Percent | 1.58% |
| Net Assets | $ 129,923,775 |
| Holdings Count | Holding | 215 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 129,923,775 Average Effective Maturity (yrs): 15.6 Total Number of Holdings: 215 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 3 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Healthcare Revenue - Hospitals 16.4 % State & Local Agencies 13.1 % General Obligations - General Purpose 12.0 % Single Family Housing - State 10.4 % Multi-Family Housing Revenue 9.5 % Transportation - Special Tax 5.0 % Universities - Colleges 4.1 % Tax Assessment 3.9 % Healthcare Revenue - Long Term Care 2.7 % Universities - Dormitories 2.6 % Other Industries 20.3 % Composition including fixed income credit quality AAA 13.6 % AA 33.8 % A 26.5 % BBB 12.6 % BB 0.9 % B 0.2 % CCC 0.1 % Not Rated 9.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169769 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Maryland Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MMDIX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.58 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.58% |
| Net Assets | $ 129,923,775 |
| Holdings Count | Holding | 215 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 129,923,775 Average Effective Maturity (yrs): 15.6 Total Number of Holdings: 215 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 3 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Healthcare Revenue - Hospitals 16.4 % State & Local Agencies 13.1 % General Obligations - General Purpose 12.0 % Single Family Housing - State 10.4 % Multi-Family Housing Revenue 9.5 % Transportation - Special Tax 5.0 % Universities - Colleges 4.1 % Tax Assessment 3.9 % Healthcare Revenue - Long Term Care 2.7 % Universities - Dormitories 2.6 % Other Industries 20.3 % Composition including fixed income credit quality AAA 13.6 % AA 33.8 % A 26.5 % BBB 12.6 % BB 0.9 % B 0.2 % CCC 0.1 % Not Rated 9.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194249 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Maryland Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPMDX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.52 % |
| Expenses Paid, Amount | $ 27 |
| Expense Ratio, Percent | 0.52% |
| Net Assets | $ 129,923,775 |
| Holdings Count | Holding | 215 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 129,923,775 Average Effective Maturity (yrs): 15.6 Total Number of Holdings: 215 Average Effective Duration (yrs): 6.4 Portfolio Turnover Rate (%): 3 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Healthcare Revenue - Hospitals 16.4 % State & Local Agencies 13.1 % General Obligations - General Purpose 12.0 % Single Family Housing - State 10.4 % Multi-Family Housing Revenue 9.5 % Transportation - Special Tax 5.0 % Universities - Colleges 4.1 % Tax Assessment 3.9 % Healthcare Revenue - Long Term Care 2.7 % Universities - Dormitories 2.6 % Other Industries 20.3 % Composition including fixed income credit quality AAA 13.6 % AA 33.8 % A 26.5 % BBB 12.6 % BB 0.9 % B 0.2 % CCC 0.1 % Not Rated 9.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006989 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Mississippi Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MISSX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.85 % |
| Expenses Paid, Amount | $ 43 |
| Expense Ratio, Percent | 0.85% |
| Net Assets | $ 74,571,959 |
| Holdings Count | Holding | 161 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 74,571,959 Average Effective Maturity (yrs): 17.1 Total Number of Holdings: 161 Average Effective Duration (yrs): 7.1 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.4 % Money Market Funds 0.6 % Industries General Obligations - General Purpose 18.5 % Universities - Colleges 13.3 % General Obligations - Schools 11.7 % Single Family Housing - State 11.2 % Water & Sewer Utility Revenue 9.1 % Healthcare Revenue - Hospitals 6.4 % State & Local Agencies 6.0 % Sales & Excise Tax Revenue 5.7 % Tax - Other 4.2 % Utilities - Municipal Owned 2.6 % Other Industries 11.3 % Composition including fixed income credit quality AAA 11.2 % AA 52.7 % A 19.0 % BBB 8.0 % BB 1.0 % Not Rated 7.5 % Money Market Funds 0.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006990 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Mississippi Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBMSX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.50 % |
| Expenses Paid, Amount | $ 76 |
| Expense Ratio, Percent | 1.50% |
| Net Assets | $ 74,571,959 |
| Holdings Count | Holding | 161 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 74,571,959 Average Effective Maturity (yrs): 17.1 Total Number of Holdings: 161 Average Effective Duration (yrs): 7.1 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.4 % Money Market Funds 0.6 % Industries General Obligations - General Purpose 18.5 % Universities - Colleges 13.3 % General Obligations - Schools 11.7 % Single Family Housing - State 11.2 % Water & Sewer Utility Revenue 9.1 % Healthcare Revenue - Hospitals 6.4 % State & Local Agencies 6.0 % Sales & Excise Tax Revenue 5.7 % Tax - Other 4.2 % Utilities - Municipal Owned 2.6 % Other Industries 11.3 % Composition including fixed income credit quality AAA 11.2 % AA 52.7 % A 19.0 % BBB 8.0 % BB 1.0 % Not Rated 7.5 % Money Market Funds 0.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169771 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Mississippi Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MMSTX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.75 % |
| Expenses Paid, Amount | $ 38 |
| Expense Ratio, Percent | 0.75% |
| Net Assets | $ 74,571,959 |
| Holdings Count | Holding | 161 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 74,571,959 Average Effective Maturity (yrs): 17.1 Total Number of Holdings: 161 Average Effective Duration (yrs): 7.1 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.4 % Money Market Funds 0.6 % Industries General Obligations - General Purpose 18.5 % Universities - Colleges 13.3 % General Obligations - Schools 11.7 % Single Family Housing - State 11.2 % Water & Sewer Utility Revenue 9.1 % Healthcare Revenue - Hospitals 6.4 % State & Local Agencies 6.0 % Sales & Excise Tax Revenue 5.7 % Tax - Other 4.2 % Utilities - Municipal Owned 2.6 % Other Industries 11.3 % Composition including fixed income credit quality AAA 11.2 % AA 52.7 % A 19.0 % BBB 8.0 % BB 1.0 % Not Rated 7.5 % Money Market Funds 0.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194252 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Mississippi Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPMSX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.69 % |
| Expenses Paid, Amount | $ 35 |
| Expense Ratio, Percent | 0.69% |
| Net Assets | $ 74,571,959 |
| Holdings Count | Holding | 161 |
| Investment Company Portfolio Turnover | 7% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 74,571,959 Average Effective Maturity (yrs): 17.1 Total Number of Holdings: 161 Average Effective Duration (yrs): 7.1 Portfolio Turnover Rate (%): 7 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.4 % Money Market Funds 0.6 % Industries General Obligations - General Purpose 18.5 % Universities - Colleges 13.3 % General Obligations - Schools 11.7 % Single Family Housing - State 11.2 % Water & Sewer Utility Revenue 9.1 % Healthcare Revenue - Hospitals 6.4 % State & Local Agencies 6.0 % Sales & Excise Tax Revenue 5.7 % Tax - Other 4.2 % Utilities - Municipal Owned 2.6 % Other Industries 11.3 % Composition including fixed income credit quality AAA 11.2 % AA 52.7 % A 19.0 % BBB 8.0 % BB 1.0 % Not Rated 7.5 % Money Market Funds 0.6 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006991 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class A |
| Trading Symbol | MFIAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.74 % |
| Expenses Paid, Amount | $ 38 |
| Expense Ratio, Percent | 0.74% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000042676 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class A1 |
| Trading Symbol | MMIDX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A1 $ 0.49 % |
| Expenses Paid, Amount | $ 25 |
| Expense Ratio, Percent | 0.49% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006992 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class B |
| Trading Symbol | MMIBX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.49 % |
| Expenses Paid, Amount | $ 76 |
| Expense Ratio, Percent | 1.49% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000042677 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class B1 |
| Trading Symbol | MMIGX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B1 $ 1.24 % |
| Expenses Paid, Amount | $ 63 |
| Expense Ratio, Percent | 1.24% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006993 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class C |
| Trading Symbol | MMICX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.49 % |
| Expenses Paid, Amount | $ 76 |
| Expense Ratio, Percent | 1.49% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000105400 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class I |
| Trading Symbol | MIMIX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.49 % |
| Expenses Paid, Amount | $ 25 |
| Expense Ratio, Percent | 0.49% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194254 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Income Fund |
| Class Name | Class R6 |
| Trading Symbol | MPMNX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.42 % |
| Expenses Paid, Amount | $ 22 |
| Expense Ratio, Percent | 0.42% |
| Net Assets | $ 5,620,604,602 |
| Holdings Count | Holding | 2,040 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 5,620,604,602 Average Effective Maturity (yrs): 19.0 Total Number of Holdings: 2,040 Average Effective Duration (yrs): 7.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.1 % Money Market Funds 2.9 % Industries Healthcare Revenue - Hospitals 17.0 % Multi-Family Housing Revenue 8.0 % Airport Revenue 7.3 % Utilities - Other 6.2 % Single Family Housing - State 5.3 % Miscellaneous Revenue - Other 4.8 % Healthcare Revenue - Long Term Care 4.8 % General Obligations - Schools 4.5 % Universities - Colleges 4.1 % Student Loan Revenue 4.0 % Other Industries 34.0 % Composition including fixed income credit quality AAA 7.0 % AA 26.8 % A 30.8 % BBB 16.6 % BB 4.6 % B 0.3 % CCC 0.1 % CC 0.2 % Not Rated 10.7 % Money Market Funds 2.9 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000227170 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Intermediate Fund |
| Class Name | Class A |
| Trading Symbol | MIUAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.69 % |
| Expenses Paid, Amount | $ 35 |
| Expense Ratio, Percent | 0.69% |
| Net Assets | $ 202,680,786 |
| Holdings Count | Holding | 460 |
| Investment Company Portfolio Turnover | 11% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 202,680,786 Average Effective Maturity (yrs): 9.7 Total Number of Holdings: 460 Average Effective Duration (yrs): 5.4 Portfolio Turnover Rate (%): 11 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Multi-Family Housing Revenue 12.6 % Student Loan Revenue 9.0 % Healthcare Revenue - Long Term Care 8.6 % Healthcare Revenue - Hospitals 7.8 % Airport Revenue 6.4 % Utilities - Other 6.3 % Universities - Colleges 6.2 % Utilities - Investor Owned 5.2 % Single Family Housing - State 4.5 % Secondary Schools 4.2 % Other Industries 29.2 % Composition including fixed income credit quality AAA 7.7 % AA 22.6 % A 29.7 % BBB 22.0 % BB 6.5 % B 0.2 % CC 0.0 % D 0.0 % Not Rated 8.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000227169 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Intermediate Fund |
| Class Name | Class C |
| Trading Symbol | MIUCX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) C $ 1.44 % |
| Expenses Paid, Amount | $ 73 |
| Expense Ratio, Percent | 1.44% |
| Net Assets | $ 202,680,786 |
| Holdings Count | Holding | 460 |
| Investment Company Portfolio Turnover | 11% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 202,680,786 Average Effective Maturity (yrs): 9.7 Total Number of Holdings: 460 Average Effective Duration (yrs): 5.4 Portfolio Turnover Rate (%): 11 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Multi-Family Housing Revenue 12.6 % Student Loan Revenue 9.0 % Healthcare Revenue - Long Term Care 8.6 % Healthcare Revenue - Hospitals 7.8 % Airport Revenue 6.4 % Utilities - Other 6.3 % Universities - Colleges 6.2 % Utilities - Investor Owned 5.2 % Single Family Housing - State 4.5 % Secondary Schools 4.2 % Other Industries 29.2 % Composition including fixed income credit quality AAA 7.7 % AA 22.6 % A 29.7 % BBB 22.0 % BB 6.5 % B 0.2 % CC 0.0 % D 0.0 % Not Rated 8.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000227171 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Intermediate Fund |
| Class Name | Class I |
| Trading Symbol | MIUIX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.44 % |
| Expenses Paid, Amount | $ 22 |
| Expense Ratio, Percent | 0.44% |
| Net Assets | $ 202,680,786 |
| Holdings Count | Holding | 460 |
| Investment Company Portfolio Turnover | 11% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 202,680,786 Average Effective Maturity (yrs): 9.7 Total Number of Holdings: 460 Average Effective Duration (yrs): 5.4 Portfolio Turnover Rate (%): 11 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Multi-Family Housing Revenue 12.6 % Student Loan Revenue 9.0 % Healthcare Revenue - Long Term Care 8.6 % Healthcare Revenue - Hospitals 7.8 % Airport Revenue 6.4 % Utilities - Other 6.3 % Universities - Colleges 6.2 % Utilities - Investor Owned 5.2 % Single Family Housing - State 4.5 % Secondary Schools 4.2 % Other Industries 29.2 % Composition including fixed income credit quality AAA 7.7 % AA 22.6 % A 29.7 % BBB 22.0 % BB 6.5 % B 0.2 % CC 0.0 % D 0.0 % Not Rated 8.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000227172 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Municipal Intermediate Fund |
| Class Name | Class R6 |
| Trading Symbol | MIURX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.38 % |
| Expenses Paid, Amount | $ 19 |
| Expense Ratio, Percent | 0.38% |
| Net Assets | $ 202,680,786 |
| Holdings Count | Holding | 460 |
| Investment Company Portfolio Turnover | 11% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 202,680,786 Average Effective Maturity (yrs): 9.7 Total Number of Holdings: 460 Average Effective Duration (yrs): 5.4 Portfolio Turnover Rate (%): 11 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.0 % Money Market Funds 3.0 % Industries Multi-Family Housing Revenue 12.6 % Student Loan Revenue 9.0 % Healthcare Revenue - Long Term Care 8.6 % Healthcare Revenue - Hospitals 7.8 % Airport Revenue 6.4 % Utilities - Other 6.3 % Universities - Colleges 6.2 % Utilities - Investor Owned 5.2 % Single Family Housing - State 4.5 % Secondary Schools 4.2 % Other Industries 29.2 % Composition including fixed income credit quality AAA 7.7 % AA 22.6 % A 29.7 % BBB 22.0 % BB 6.5 % B 0.2 % CC 0.0 % D 0.0 % Not Rated 8.3 % Money Market Funds 3.0 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006987 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Massachusetts Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFSSX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.82 % |
| Expenses Paid, Amount | $ 42 |
| Expense Ratio, Percent | 0.82% |
| Net Assets | $ 377,733,105 |
| Holdings Count | Holding | 279 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 377,733,105 Average Effective Maturity (yrs): 16.7 Total Number of Holdings: 279 Average Effective Duration (yrs): 6.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.9 % Money Market Funds 2.1 % Industries Universities - Colleges 19.6 % Healthcare Revenue - Hospitals 16.3 % General Obligations - General Purpose 13.6 % Multi-Family Housing Revenue 7.0 % Student Loan Revenue 6.1 % Airport Revenue 6.0 % Sales & Excise Tax Revenue 5.7 % Single Family Housing - State 4.8 % Transportation - Special Tax 4.3 % Utilities - Other 3.9 % Other Industries 12.7 % Composition including fixed income credit quality AAA 4.1 % AA 46.3 % A 18.8 % BBB 20.6 % BB 1.9 % B 0.6 % CC 0.1 % Not Rated 5.5 % Money Market Funds 2.1 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006988 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Massachusetts Municipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBMAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.57 % |
| Expenses Paid, Amount | $ 80 |
| Expense Ratio, Percent | 1.57% |
| Net Assets | $ 377,733,105 |
| Holdings Count | Holding | 279 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 377,733,105 Average Effective Maturity (yrs): 16.7 Total Number of Holdings: 279 Average Effective Duration (yrs): 6.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.9 % Money Market Funds 2.1 % Industries Universities - Colleges 19.6 % Healthcare Revenue - Hospitals 16.3 % General Obligations - General Purpose 13.6 % Multi-Family Housing Revenue 7.0 % Student Loan Revenue 6.1 % Airport Revenue 6.0 % Sales & Excise Tax Revenue 5.7 % Single Family Housing - State 4.8 % Transportation - Special Tax 4.3 % Utilities - Other 3.9 % Other Industries 12.7 % Composition including fixed income credit quality AAA 4.1 % AA 46.3 % A 18.8 % BBB 20.6 % BB 1.9 % B 0.6 % CC 0.1 % Not Rated 5.5 % Money Market Funds 2.1 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169770 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Massachusetts Municipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MTALX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.57 % |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.57% |
| Net Assets | $ 377,733,105 |
| Holdings Count | Holding | 279 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 377,733,105 Average Effective Maturity (yrs): 16.7 Total Number of Holdings: 279 Average Effective Duration (yrs): 6.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.9 % Money Market Funds 2.1 % Industries Universities - Colleges 19.6 % Healthcare Revenue - Hospitals 16.3 % General Obligations - General Purpose 13.6 % Multi-Family Housing Revenue 7.0 % Student Loan Revenue 6.1 % Airport Revenue 6.0 % Sales & Excise Tax Revenue 5.7 % Single Family Housing - State 4.8 % Transportation - Special Tax 4.3 % Utilities - Other 3.9 % Other Industries 12.7 % Composition including fixed income credit quality AAA 4.1 % AA 46.3 % A 18.8 % BBB 20.6 % BB 1.9 % B 0.6 % CC 0.1 % Not Rated 5.5 % Money Market Funds 2.1 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194250 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Massachusetts Municipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPMAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.50 % |
| Expenses Paid, Amount | $ 26 |
| Expense Ratio, Percent | 0.50% |
| Net Assets | $ 377,733,105 |
| Holdings Count | Holding | 279 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 377,733,105 Average Effective Maturity (yrs): 16.7 Total Number of Holdings: 279 Average Effective Duration (yrs): 6.5 Portfolio Turnover Rate (%): 5 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 97.9 % Money Market Funds 2.1 % Industries Universities - Colleges 19.6 % Healthcare Revenue - Hospitals 16.3 % General Obligations - General Purpose 13.6 % Multi-Family Housing Revenue 7.0 % Student Loan Revenue 6.1 % Airport Revenue 6.0 % Sales & Excise Tax Revenue 5.7 % Single Family Housing - State 4.8 % Transportation - Special Tax 4.3 % Utilities - Other 3.9 % Other Industries 12.7 % Composition including fixed income credit quality AAA 4.1 % AA 46.3 % A 18.8 % BBB 20.6 % BB 1.9 % B 0.6 % CC 0.1 % Not Rated 5.5 % Money Market Funds 2.1 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006965 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® Pennsylvania Municipal Bond Fund |
| Class Name | Class A |
| Trading Symbol | MFPAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) A $ 0.69 % |
| Expenses Paid, Amount | $ 35 |
| Expense Ratio, Percent | 0.69% |
| Net Assets | $ 165,757,753 |
| Holdings Count | Holding | 243 |
| Investment Company Portfolio Turnover | 9% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 165,757,753 Average Effective Maturity (yrs): 17.7 Total Number of Holdings: 243 Average Effective Duration (yrs): 7.2 Portfolio Turnover Rate (%): 9 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.3 % Money Market Funds 0.7 % Industries Healthcare Revenue - Hospitals 15.3 % Universities - Colleges 13.6 % General Obligations - Schools 10.2 % Single Family Housing - State 8.7 % General Obligations - General Purpose 7.9 % Water & Sewer Utility Revenue 7.7 % Healthcare Revenue - Long Term Care 4.7 % Student Loan Revenue 4.1 % Tax - Other 3.7 % Airport Revenue 3.5 % Other Industries 20.6 % Composition including fixed income credit quality AAA 1.6 % AA 35.5 % A 37.8 % BBB 13.3 % BB 3.5 % B 0.7 % CC 0.0 % Not Rated 6.9 % Money Market Funds 0.7 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000006966 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® PennsylvaniaMunicipal Bond Fund |
| Class Name | Class B |
| Trading Symbol | MBPAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) B $ 1.44 % |
| Expenses Paid, Amount | $ 74 |
| Expense Ratio, Percent | 1.44% |
| Net Assets | $ 165,757,753 |
| Holdings Count | Holding | 243 |
| Investment Company Portfolio Turnover | 9% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 165,757,753 Average Effective Maturity (yrs): 17.7 Total Number of Holdings: 243 Average Effective Duration (yrs): 7.2 Portfolio Turnover Rate (%): 9 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.3 % Money Market Funds 0.7 % Industries Healthcare Revenue - Hospitals 15.3 % Universities - Colleges 13.6 % General Obligations - Schools 10.2 % Single Family Housing - State 8.7 % General Obligations - General Purpose 7.9 % Water & Sewer Utility Revenue 7.7 % Healthcare Revenue - Long Term Care 4.7 % Student Loan Revenue 4.1 % Tax - Other 3.7 % Airport Revenue 3.5 % Other Industries 20.6 % Composition including fixed income credit quality AAA 1.6 % AA 35.5 % A 37.8 % BBB 13.3 % BB 3.5 % B 0.7 % CC 0.0 % Not Rated 6.9 % Money Market Funds 0.7 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000169761 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® PennsylvaniaMunicipal Bond Fund |
| Class Name | Class I |
| Trading Symbol | MPALX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) I $ 0.59 % |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.59% |
| Net Assets | $ 165,757,753 |
| Holdings Count | Holding | 243 |
| Investment Company Portfolio Turnover | 9% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 165,757,753 Average Effective Maturity (yrs): 17.7 Total Number of Holdings: 243 Average Effective Duration (yrs): 7.2 Portfolio Turnover Rate (%): 9 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.3 % Money Market Funds 0.7 % Industries Healthcare Revenue - Hospitals 15.3 % Universities - Colleges 13.6 % General Obligations - Schools 10.2 % Single Family Housing - State 8.7 % General Obligations - General Purpose 7.9 % Water & Sewer Utility Revenue 7.7 % Healthcare Revenue - Long Term Care 4.7 % Student Loan Revenue 4.1 % Tax - Other 3.7 % Airport Revenue 3.5 % Other Industries 20.6 % Composition including fixed income credit quality AAA 1.6 % AA 35.5 % A 37.8 % BBB 13.3 % BB 3.5 % B 0.7 % CC 0.0 % Not Rated 6.9 % Money Market Funds 0.7 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| C000194232 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | MFS® PennsylvaniaMunicipal Bond Fund |
| Class Name | Class R6 |
| Trading Symbol | MPPAX |
| Annual or Semi-Annual Statement [Text Block] | This semiannual shareholder report |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the fund at funds.mfs.com |
| Additional Information Phone Number | 1‑800‑225‑2606 |
| Additional Information Email | orderliterature@mfs.com |
| Additional Information Website | funds.mfs.com |
| Expenses [Text Block] | FUND EXPENSES What were the fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment (annualized) R6 $ 0.52 % |
| Expenses Paid, Amount | $ 27 |
| Expense Ratio, Percent | 0.52% |
| Net Assets | $ 165,757,753 |
| Holdings Count | Holding | 243 |
| Investment Company Portfolio Turnover | 9% |
| Additional Fund Statistics [Text Block] | FUND STATISTICS AS OF 9/30/24 Net Assets ($): 165,757,753 Average Effective Maturity (yrs): 17.7 Total Number of Holdings: 243 Average Effective Duration (yrs): 7.2 Portfolio Turnover Rate (%): 9 Where the fund holds derivatives, they are not included in the total number of portfolio holdings. |
| Holdings [Text Block] | PORTFOLIO COMPOSITION (BASED ON TOTAL INVESTMENTS AS OF 9/30/24) Portfolio structure Fixed Income 99.3 % Money Market Funds 0.7 % Industries Healthcare Revenue - Hospitals 15.3 % Universities - Colleges 13.6 % General Obligations - Schools 10.2 % Single Family Housing - State 8.7 % General Obligations - General Purpose 7.9 % Water & Sewer Utility Revenue 7.7 % Healthcare Revenue - Long Term Care 4.7 % Student Loan Revenue 4.1 % Tax - Other 3.7 % Airport Revenue 3.5 % Other Industries 20.6 % Composition including fixed income credit quality AAA 1.6 % AA 35.5 % A 37.8 % BBB 13.3 % BB 3.5 % B 0.7 % CC 0.0 % Not Rated 6.9 % Money Market Funds 0.7 % Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. For purposes of these classifications, MFS uses its own internal sector/industry classification methodology, which may deviate from classification methodologies used by other industry participants (e.g., the Global Industry Classification Standard). |
| Credit Ratings Selection [Text Block] | Ratings are assigned using Moody’s, Fitch, and Standard & Poor’s and applying a hierarchy: If all 3 agencies rate a security, the middle rating is assigned; if 2 agencies rate a security, the lower rating is assigned. If none of the 3 agencies rate a security, we use DBRS Morningstar. If none of the 4 agencies rate a security, we use Kroll Bond Rating Agency. Ratings are shown in the S&P and Fitch scale (e.g., AAA). All ratings are subject to change. |
| Shareholder Report, Holdings (Details) | Sep. 30, 2024 |
| C000006957 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36.40% |
| C000006957 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36% |
| C000006957 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.60% |
| C000006957 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006957 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006957 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000006957 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006957 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006957 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.50% |
| C000006957 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.10% |
| C000006957 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000006957 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000006957 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11% |
| C000006957 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006957 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000006957 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000006957 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006957 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006957 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000006957 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000006957 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006958 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36.40% |
| C000006958 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36% |
| C000006958 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.60% |
| C000006958 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006958 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006958 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000006958 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006958 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006958 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.50% |
| C000006958 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.10% |
| C000006958 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000006958 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000006958 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11% |
| C000006958 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006958 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000006958 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000006958 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006958 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006958 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000006958 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000006958 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169758 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36.40% |
| C000169758 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36% |
| C000169758 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.60% |
| C000169758 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000169758 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000169758 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000169758 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000169758 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169758 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.50% |
| C000169758 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.10% |
| C000169758 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000169758 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000169758 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11% |
| C000169758 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000169758 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000169758 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000169758 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000169758 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000169758 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000169758 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000169758 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194226 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36.40% |
| C000194226 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 36% |
| C000194226 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.60% |
| C000194226 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000194226 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194226 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000194226 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000194226 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194226 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.50% |
| C000194226 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.10% |
| C000194226 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000194226 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000194226 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11% |
| C000194226 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000194226 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000194226 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.60% |
| C000194226 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000194226 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000194226 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000194226 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000194226 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006959 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.30% |
| C000006959 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000006959 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.60% |
| C000006959 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006959 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006959 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006959 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006959 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006959 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000006959 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006959 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000006959 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000006959 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006959 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006959 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006959 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006959 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006959 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006959 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000006959 [Member] | Industrial Revenue Airlines [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006959 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006959 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.10% |
| C000006959 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006960 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.30% |
| C000006960 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000006960 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.60% |
| C000006960 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006960 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006960 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006960 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006960 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006960 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000006960 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006960 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000006960 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000006960 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006960 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006960 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006960 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006960 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006960 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006960 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000006960 [Member] | Industrial Revenue Airlines [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006960 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006960 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.10% |
| C000006960 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006961 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.30% |
| C000006961 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000006961 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.60% |
| C000006961 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006961 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006961 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006961 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006961 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006961 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000006961 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006961 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000006961 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000006961 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006961 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006961 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006961 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006961 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006961 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006961 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000006961 [Member] | Industrial Revenue Airlines [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006961 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006961 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.10% |
| C000006961 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169759 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.30% |
| C000169759 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000169759 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.60% |
| C000169759 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000169759 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000169759 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000169759 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000169759 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000169759 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000169759 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169759 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000169759 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000169759 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000169759 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000169759 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000169759 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000169759 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000169759 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000169759 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000169759 [Member] | Industrial Revenue Airlines [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000169759 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000169759 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.10% |
| C000169759 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194228 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.30% |
| C000194228 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000194228 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.60% |
| C000194228 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000194228 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000194228 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000194228 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000194228 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000194228 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.10% |
| C000194228 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194228 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000194228 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000194228 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000194228 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000194228 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000194228 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000194228 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000194228 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000194228 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000194228 [Member] | Industrial Revenue Airlines [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000194228 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000194228 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.10% |
| C000194228 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006962 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 50% |
| C000006962 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006962 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006962 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006962 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000006962 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006962 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000006962 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006962 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006962 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.80% |
| C000006962 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000006962 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000006962 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006962 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.90% |
| C000006962 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006962 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.10% |
| C000006962 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006962 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000006962 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006962 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006962 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000006962 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006963 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 50% |
| C000006963 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006963 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006963 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006963 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000006963 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006963 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000006963 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006963 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006963 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.80% |
| C000006963 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000006963 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000006963 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006963 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.90% |
| C000006963 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006963 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.10% |
| C000006963 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006963 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000006963 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006963 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006963 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000006963 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006964 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 50% |
| C000006964 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006964 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006964 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000006964 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000006964 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006964 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000006964 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006964 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006964 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.80% |
| C000006964 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000006964 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000006964 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006964 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.90% |
| C000006964 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006964 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.10% |
| C000006964 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006964 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000006964 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006964 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006964 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000006964 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169760 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 50% |
| C000169760 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000169760 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000169760 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000169760 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000169760 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169760 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000169760 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000169760 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169760 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.80% |
| C000169760 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000169760 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000169760 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000169760 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.90% |
| C000169760 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000169760 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.10% |
| C000169760 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000169760 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000169760 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000169760 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000169760 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000169760 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194230 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 50% |
| C000194230 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000194230 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000194230 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.10% |
| C000194230 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000194230 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194230 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000194230 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000194230 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194230 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.80% |
| C000194230 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.20% |
| C000194230 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000194230 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000194230 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.90% |
| C000194230 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000194230 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.10% |
| C000194230 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000194230 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.80% |
| C000194230 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000194230 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000194230 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.40% |
| C000194230 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006967 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.30% |
| C000006967 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.60% |
| C000006967 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006967 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.40% |
| C000006967 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006967 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006967 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006967 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006967 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006967 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 21.10% |
| C000006967 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006967 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006967 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006967 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006967 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006967 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.90% |
| C000006967 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006967 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006967 [Member] | Port Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006967 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000006967 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000006967 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006968 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.30% |
| C000006968 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.60% |
| C000006968 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006968 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.40% |
| C000006968 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006968 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006968 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006968 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006968 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006968 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 21.10% |
| C000006968 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006968 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006968 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006968 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006968 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006968 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.90% |
| C000006968 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006968 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006968 [Member] | Port Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006968 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000006968 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000006968 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000169762 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.30% |
| C000169762 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.60% |
| C000169762 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000169762 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.40% |
| C000169762 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169762 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169762 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000169762 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000169762 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000169762 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 21.10% |
| C000169762 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000169762 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000169762 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000169762 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000169762 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000169762 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.90% |
| C000169762 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000169762 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000169762 [Member] | Port Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000169762 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000169762 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000169762 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000194234 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.30% |
| C000194234 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.60% |
| C000194234 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000194234 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.40% |
| C000194234 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194234 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194234 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000194234 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000194234 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000194234 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 21.10% |
| C000194234 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000194234 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000194234 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000194234 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000194234 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000194234 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.90% |
| C000194234 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000194234 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000194234 [Member] | Port Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000194234 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.90% |
| C000194234 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000194234 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006971 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.10% |
| C000006971 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.10% |
| C000006971 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006971 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000006971 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006971 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006971 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006971 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006971 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.50% |
| C000006971 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006971 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006971 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006971 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000006971 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000006971 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006971 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006971 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000006971 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006971 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006971 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006971 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006971 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000006971 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006972 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.10% |
| C000006972 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.10% |
| C000006972 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006972 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000006972 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006972 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006972 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006972 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006972 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.50% |
| C000006972 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006972 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006972 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006972 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000006972 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000006972 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006972 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006972 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000006972 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006972 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006972 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006972 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006972 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000006972 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006973 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.10% |
| C000006973 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.10% |
| C000006973 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006973 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000006973 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006973 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006973 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006973 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006973 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.50% |
| C000006973 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006973 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000006973 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000006973 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000006973 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000006973 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006973 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006973 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000006973 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006973 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006973 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006973 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006973 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000006973 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000169764 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.10% |
| C000169764 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.10% |
| C000169764 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000169764 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000169764 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000169764 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000169764 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000169764 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000169764 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.50% |
| C000169764 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000169764 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000169764 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000169764 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000169764 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000169764 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000169764 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000169764 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000169764 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000169764 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000169764 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000169764 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000169764 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000169764 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000194238 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.10% |
| C000194238 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.10% |
| C000194238 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000194238 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.50% |
| C000194238 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194238 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000194238 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000194238 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000194238 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17.50% |
| C000194238 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000194238 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.20% |
| C000194238 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000194238 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000194238 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000194238 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000194238 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000194238 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000194238 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000194238 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000194238 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000194238 [Member] | Toll Roads [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000194238 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.10% |
| C000194238 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006974 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000006974 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34.90% |
| C000006974 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000006974 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000006974 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006974 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000006974 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006974 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000006974 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000006974 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000006974 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000006974 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006974 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006974 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006974 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006974 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000006974 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.40% |
| C000006974 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006974 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000006974 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.80% |
| C000006974 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000006975 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000006975 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34.90% |
| C000006975 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000006975 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000006975 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006975 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000006975 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006975 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000006975 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000006975 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000006975 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000006975 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006975 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006975 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006975 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006975 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000006975 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.40% |
| C000006975 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000006975 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000006975 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.80% |
| C000006975 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000169765 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000169765 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34.90% |
| C000169765 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000169765 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000169765 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169765 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000169765 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000169765 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000169765 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000169765 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000169765 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000169765 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000169765 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000169765 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000169765 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000169765 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000169765 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.40% |
| C000169765 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000169765 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000169765 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.80% |
| C000169765 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000194240 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000194240 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34.90% |
| C000194240 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000194240 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.50% |
| C000194240 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194240 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000194240 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000194240 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000194240 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000194240 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000194240 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000194240 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000194240 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000194240 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000194240 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000194240 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000194240 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.40% |
| C000194240 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.10% |
| C000194240 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000194240 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.80% |
| C000194240 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.20% |
| C000006976 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 57.50% |
| C000006976 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.90% |
| C000006976 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000006976 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006976 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006976 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006976 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006976 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10% |
| C000006976 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13% |
| C000006976 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.20% |
| C000006976 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006976 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006976 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.50% |
| C000006976 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000006976 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006976 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000006976 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006976 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006976 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.80% |
| C000006976 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006977 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 57.50% |
| C000006977 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.90% |
| C000006977 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000006977 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000006977 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006977 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006977 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006977 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10% |
| C000006977 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13% |
| C000006977 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.20% |
| C000006977 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006977 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006977 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.50% |
| C000006977 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000006977 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006977 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000006977 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006977 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006977 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.80% |
| C000006977 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000169766 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 57.50% |
| C000169766 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.90% |
| C000169766 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000169766 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000169766 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169766 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000169766 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000169766 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10% |
| C000169766 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13% |
| C000169766 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.20% |
| C000169766 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169766 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000169766 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.50% |
| C000169766 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000169766 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169766 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000169766 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000169766 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000169766 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.80% |
| C000169766 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000194242 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 57.50% |
| C000194242 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.90% |
| C000194242 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.90% |
| C000194242 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000194242 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194242 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000194242 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000194242 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10% |
| C000194242 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13% |
| C000194242 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.20% |
| C000194242 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194242 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000194242 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.50% |
| C000194242 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.80% |
| C000194242 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194242 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.80% |
| C000194242 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000194242 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000194242 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 98.80% |
| C000194242 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006978 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.80% |
| C000006978 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 24.10% |
| C000006978 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006978 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006978 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006978 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006978 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006978 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006978 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 25.10% |
| C000006978 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006978 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006978 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000006978 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006978 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000006978 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006978 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000006978 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000006978 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006978 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.80% |
| C000006978 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000006978 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006979 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.80% |
| C000006979 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 24.10% |
| C000006979 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006979 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006979 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006979 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006979 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006979 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006979 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 25.10% |
| C000006979 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006979 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006979 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000006979 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006979 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000006979 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006979 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000006979 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000006979 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006979 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.80% |
| C000006979 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000006979 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006980 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.80% |
| C000006980 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 24.10% |
| C000006980 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000006980 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006980 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006980 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000006980 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006980 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006980 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 25.10% |
| C000006980 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000006980 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006980 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000006980 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006980 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000006980 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000006980 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000006980 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000006980 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006980 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.80% |
| C000006980 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000006980 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000169767 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.80% |
| C000169767 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 24.10% |
| C000169767 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000169767 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000169767 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000169767 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000169767 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000169767 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000169767 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 25.10% |
| C000169767 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000169767 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000169767 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000169767 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000169767 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000169767 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000169767 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000169767 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000169767 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000169767 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.80% |
| C000169767 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000169767 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000194244 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 32.80% |
| C000194244 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 24.10% |
| C000194244 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.80% |
| C000194244 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000194244 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000194244 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000194244 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000194244 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000194244 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 25.10% |
| C000194244 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.60% |
| C000194244 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000194244 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.60% |
| C000194244 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000194244 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000194244 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14% |
| C000194244 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000194244 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000194244 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000194244 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.80% |
| C000194244 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 96.70% |
| C000194244 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000006983 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 31.50% |
| C000006983 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.70% |
| C000006983 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000006983 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006983 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006983 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006983 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006983 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000006983 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006983 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.60% |
| C000006983 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000006983 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000006983 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006983 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000006983 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000006983 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000006983 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006983 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006983 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006983 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006983 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.70% |
| C000006983 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006984 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 31.50% |
| C000006984 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.70% |
| C000006984 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000006984 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000006984 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006984 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006984 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000006984 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000006984 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006984 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.60% |
| C000006984 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000006984 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000006984 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000006984 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000006984 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000006984 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000006984 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006984 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006984 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006984 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000006984 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.70% |
| C000006984 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000169768 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 31.50% |
| C000169768 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.70% |
| C000169768 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000169768 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000169768 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000169768 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169768 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000169768 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000169768 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000169768 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.60% |
| C000169768 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000169768 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000169768 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000169768 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000169768 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000169768 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000169768 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000169768 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000169768 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000169768 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000169768 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.70% |
| C000169768 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000194246 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 31.50% |
| C000194246 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.70% |
| C000194246 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.90% |
| C000194246 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| C000194246 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194246 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194246 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.60% |
| C000194246 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000194246 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000194246 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.60% |
| C000194246 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000194246 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.60% |
| C000194246 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.40% |
| C000194246 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000194246 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000194246 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000194246 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000194246 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000194246 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000194246 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.60% |
| C000194246 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.70% |
| C000194246 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.30% |
| C000006985 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 33.80% |
| C000006985 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.50% |
| C000006985 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000006985 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006985 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000006985 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006985 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000006985 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006985 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000006985 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000006985 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006985 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000006985 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.40% |
| C000006985 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000006985 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000006985 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000006985 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000006985 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006985 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006985 [Member] | Universities Dormitories [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006985 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000006985 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000006986 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 33.80% |
| C000006986 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.50% |
| C000006986 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000006986 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000006986 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000006986 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006986 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000006986 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006986 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000006986 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000006986 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006986 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000006986 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.40% |
| C000006986 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000006986 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000006986 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000006986 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000006986 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000006986 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006986 [Member] | Universities Dormitories [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006986 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000006986 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000169769 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 33.80% |
| C000169769 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.50% |
| C000169769 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000169769 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000169769 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000169769 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000169769 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000169769 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000169769 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000169769 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000169769 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000169769 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000169769 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.40% |
| C000169769 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000169769 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000169769 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000169769 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000169769 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000169769 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169769 [Member] | Universities Dormitories [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169769 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000169769 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000194249 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 33.80% |
| C000194249 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.50% |
| C000194249 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000194249 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.90% |
| C000194249 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000194249 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194249 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.30% |
| C000194249 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000194249 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000194249 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.30% |
| C000194249 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000194249 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12% |
| C000194249 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.40% |
| C000194249 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.10% |
| C000194249 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.40% |
| C000194249 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.50% |
| C000194249 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5% |
| C000194249 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.70% |
| C000194249 [Member] | Tax Assessment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194249 [Member] | Universities Dormitories [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194249 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000194249 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000006989 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 52.70% |
| C000006989 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19% |
| C000006989 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006989 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1% |
| C000006989 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000006989 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006989 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006989 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.30% |
| C000006989 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.10% |
| C000006989 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000006989 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.50% |
| C000006989 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006989 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006989 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006989 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000006989 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006989 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000006989 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006989 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.40% |
| C000006989 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006990 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 52.70% |
| C000006990 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19% |
| C000006990 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006990 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1% |
| C000006990 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000006990 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006990 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006990 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.30% |
| C000006990 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.10% |
| C000006990 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000006990 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.50% |
| C000006990 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000006990 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006990 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000006990 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000006990 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000006990 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000006990 [Member] | Utilities Investor Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000006990 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.40% |
| C000006990 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000169771 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 52.70% |
| C000169771 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19% |
| C000169771 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000169771 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1% |
| C000169771 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000169771 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000169771 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000169771 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.30% |
| C000169771 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.10% |
| C000169771 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000169771 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.50% |
| C000169771 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000169771 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000169771 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000169771 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000169771 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000169771 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000169771 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000169771 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.40% |
| C000169771 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000194252 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 52.70% |
| C000194252 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19% |
| C000194252 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000194252 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1% |
| C000194252 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.50% |
| C000194252 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000194252 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000194252 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.30% |
| C000194252 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.10% |
| C000194252 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000194252 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.50% |
| C000194252 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000194252 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000194252 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000194252 [Member] | State And Local Agencies [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000194252 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.20% |
| C000194252 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 11.70% |
| C000194252 [Member] | Utilities Municipal Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.60% |
| C000194252 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.40% |
| C000194252 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006991 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000006991 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000006991 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006991 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006991 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000006991 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006991 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006991 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006991 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006991 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000006991 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000006991 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006991 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000006991 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000006991 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006991 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006991 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006991 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006991 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006991 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006991 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006991 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000006991 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000042676 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000042676 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000042676 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000042676 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000042676 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000042676 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000042676 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000042676 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000042676 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000042676 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000042676 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000042676 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000042676 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000042676 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000042676 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000042676 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000042676 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000042676 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000042676 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000042676 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000042676 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000042676 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000042676 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000006992 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000006992 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000006992 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006992 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006992 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000006992 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006992 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006992 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006992 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006992 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000006992 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000006992 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006992 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000006992 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000006992 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006992 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006992 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006992 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006992 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006992 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006992 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006992 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000006992 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000042677 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000042677 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000042677 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000042677 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000042677 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000042677 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000042677 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000042677 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000042677 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000042677 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000042677 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000042677 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000042677 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000042677 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000042677 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000042677 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000042677 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000042677 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000042677 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000042677 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000042677 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000042677 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000042677 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000006993 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000006993 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000006993 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000006993 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000006993 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000006993 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000006993 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006993 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000006993 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006993 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000006993 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000006993 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006993 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000006993 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000006993 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000006993 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000006993 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000006993 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000006993 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006993 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006993 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000006993 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000006993 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000105400 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000105400 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000105400 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000105400 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000105400 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000105400 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000105400 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000105400 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000105400 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000105400 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000105400 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000105400 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000105400 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000105400 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000105400 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000105400 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000105400 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000105400 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000105400 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000105400 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000105400 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000105400 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000105400 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000194254 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 26.80% |
| C000194254 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 30.80% |
| C000194254 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.60% |
| C000194254 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.60% |
| C000194254 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000194254 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.30% |
| C000194254 [Member] | Fitch, CCC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194254 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| C000194254 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000194254 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000194254 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 34% |
| C000194254 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000194254 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 17% |
| C000194254 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000194254 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.30% |
| C000194254 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000194254 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8% |
| C000194254 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.30% |
| C000194254 [Member] | Miscellaneous Revenue Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000194254 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000194254 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4% |
| C000194254 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.10% |
| C000194254 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.90% |
| C000227170 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.60% |
| C000227170 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.70% |
| C000227170 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22% |
| C000227170 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000227170 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227170 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000227170 [Member] | Fitch, D Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227170 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.30% |
| C000227170 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000227170 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227170 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.20% |
| C000227170 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000227170 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000227170 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.30% |
| C000227170 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000227170 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000227170 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000227170 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000227170 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000227170 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000227170 [Member] | Utilities Investor Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000227170 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000227170 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227169 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.60% |
| C000227169 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.70% |
| C000227169 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22% |
| C000227169 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000227169 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227169 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000227169 [Member] | Fitch, D Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227169 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.30% |
| C000227169 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000227169 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227169 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.20% |
| C000227169 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000227169 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000227169 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.30% |
| C000227169 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000227169 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000227169 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000227169 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000227169 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000227169 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000227169 [Member] | Utilities Investor Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000227169 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000227169 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227171 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.60% |
| C000227171 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.70% |
| C000227171 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22% |
| C000227171 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000227171 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227171 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000227171 [Member] | Fitch, D Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227171 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.30% |
| C000227171 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000227171 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227171 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.20% |
| C000227171 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000227171 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000227171 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.30% |
| C000227171 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000227171 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000227171 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000227171 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000227171 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000227171 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000227171 [Member] | Utilities Investor Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000227171 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000227171 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227172 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22.60% |
| C000227172 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.70% |
| C000227172 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 22% |
| C000227172 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.50% |
| C000227172 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227172 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000227172 [Member] | Fitch, D Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000227172 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.30% |
| C000227172 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000227172 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000227172 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 29.20% |
| C000227172 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000227172 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.80% |
| C000227172 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.30% |
| C000227172 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.50% |
| C000227172 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.60% |
| C000227172 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.40% |
| C000227172 [Member] | Secondary Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.20% |
| C000227172 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.60% |
| C000227172 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9% |
| C000227172 [Member] | Utilities Investor Owned [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.20% |
| C000227172 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97% |
| C000227172 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000006987 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.30% |
| C000006987 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.80% |
| C000006987 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000006987 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006987 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006987 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006987 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006987 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006987 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006987 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006987 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.60% |
| C000006987 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006987 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006987 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000006987 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006987 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006987 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006987 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006987 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000006987 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006987 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.90% |
| C000006987 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006988 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.30% |
| C000006988 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.80% |
| C000006988 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000006988 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000006988 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000006988 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000006988 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000006988 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006988 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006988 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000006988 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.60% |
| C000006988 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006988 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000006988 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000006988 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000006988 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000006988 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000006988 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000006988 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000006988 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000006988 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.90% |
| C000006988 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000169770 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.30% |
| C000169770 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.80% |
| C000169770 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000169770 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000169770 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000169770 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000169770 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000169770 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000169770 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000169770 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000169770 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.60% |
| C000169770 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000169770 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000169770 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000169770 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000169770 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000169770 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000169770 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000169770 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000169770 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000169770 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.90% |
| C000169770 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000194250 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 46.30% |
| C000194250 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.80% |
| C000194250 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000194250 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000194250 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.10% |
| C000194250 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.60% |
| C000194250 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.50% |
| C000194250 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000194250 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000194250 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 12.70% |
| C000194250 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.60% |
| C000194250 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000194250 [Member] | Sales And Excise Tax Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.70% |
| C000194250 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 16.30% |
| C000194250 [Member] | Utilities Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.90% |
| C000194250 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.80% |
| C000194250 [Member] | Multi Family Housing Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000194250 [Member] | Transportation Special Tax [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.30% |
| C000194250 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6% |
| C000194250 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000194250 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 97.90% |
| C000194250 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.10% |
| C000006965 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.50% |
| C000006965 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.80% |
| C000006965 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000006965 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000006965 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006965 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006965 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000006965 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000006965 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006965 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000006965 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006965 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006965 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.90% |
| C000006965 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006965 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.30% |
| C000006965 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.70% |
| C000006965 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.20% |
| C000006965 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000006965 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000006965 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006965 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.30% |
| C000006965 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006966 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.50% |
| C000006966 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.80% |
| C000006966 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000006966 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000006966 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000006966 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006966 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000006966 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000006966 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000006966 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000006966 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000006966 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000006966 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.90% |
| C000006966 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000006966 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.30% |
| C000006966 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.70% |
| C000006966 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.20% |
| C000006966 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000006966 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000006966 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000006966 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.30% |
| C000006966 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000169761 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.50% |
| C000169761 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.80% |
| C000169761 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000169761 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000169761 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000169761 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000169761 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000169761 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000169761 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000169761 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000169761 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000169761 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000169761 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.90% |
| C000169761 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000169761 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.30% |
| C000169761 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.70% |
| C000169761 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.20% |
| C000169761 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000169761 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000169761 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000169761 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.30% |
| C000169761 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000194232 [Member] | Fitch, AA Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.50% |
| C000194232 [Member] | Fitch, A Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 37.80% |
| C000194232 [Member] | Fitch, BBB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.30% |
| C000194232 [Member] | Fitch, BB Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000194232 [Member] | Fitch, CC Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0% |
| C000194232 [Member] | Fitch, B Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000194232 [Member] | Not Rated [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.90% |
| C000194232 [Member] | Moody's, Aaa Rating [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.60% |
| C000194232 [Member] | Money Market Funds Quality [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000194232 [Member] | Unclassified Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 20.60% |
| C000194232 [Member] | Water And Sewer Utility Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.70% |
| C000194232 [Member] | Universities Colleges [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 13.60% |
| C000194232 [Member] | General Obligations General Purpose [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7.90% |
| C000194232 [Member] | Tax Other [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000194232 [Member] | Healthcare Revenue Hospitals [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 15.30% |
| C000194232 [Member] | Single Family Housing State [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.70% |
| C000194232 [Member] | General Obligations Schools [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.20% |
| C000194232 [Member] | Airport Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.50% |
| C000194232 [Member] | Healthcare Revenue Long Term Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.70% |
| C000194232 [Member] | Student Loan Revenue [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| C000194232 [Member] | Fixed Income Securities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 99.30% |
| C000194232 [Member] | Money Market Funds [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
