| Form N-CSR Cover | 12 Months Ended |
| May 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Municipal Series Trust |
| Entity Central Index Key | 0000799113 |
| Document Period End Date | May 31, 2024 |
| Shareholder Report | 12 Months Ended |
| May 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Municipal Series Trust |
| Entity Central Index Key | 0000799113 |
| Document Period End Date | May 31, 2024 |
| C000038983 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Strategic Municipal Opportunities Fund |
| Class Name | Investor A Shares |
| Trading Symbol | MEMTX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Strategic Municipal Opportunities Fund (the “Fund”) for the period of June 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at blackrock.com/fundreports . |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | (800) 441‑7762 |
| Additional Information Website | blackrock.com/fundreports |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class name Costs of a $10,000 Costs paid as a percentage of a Investor A Shares $ 0.87 % |
| Expenses Paid, Amount | $ 89 |
| Expense Ratio, Percent | 0.87% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with the benefit of income augmented by a modest gain in prices. Declining inflation fueled expectations that the U.S. Federal Reserve was set to begin cutting interest rates in 2024, benefiting the broader fixed-income market. Municipal bonds were further helped by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. High-yield municipals performed particularly well in an environment of hearty investor risk appetites. What contributed to performance? The Fund’s use of U.S. Treasury futures to manage interest rate risk helped performance at a time in which Treasury yields rose (as prices fell). Overweight positions in AA rated securities and bonds with maturities of 20 years and longer contributed, as well. The Fund also benefited from keeping duration (interest-rate sensitivity) above that of the benchmark given the positive performance for the municipal market. Holdings in corporate-backed municipal issues, specifically pre-paid gas bonds, further contributed to results. The Fund’s use of derivatives marginally contributed to performance. What detracted from performance? A position in Puerto Rico Electric Power Authority bonds, which experienced a pronounced price decline early in the period, was a key detractor. An underweight in the healthcare sector also detracted, but to a lesser extent. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | Fund performance Cumulative performance: June 1, 2014 through May 31, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance. |
| Average Annual Return [Table Text Block] | Average annual total returns 1 Year 5 Years 10 Years Investor A Shares 3.64 ) % 0.05 ) % 1.96 % Investor A Shares (with sales charge) (0.76 ) % (0.82 ) % 1.52 % Bloomberg Municipal Bond Index 2.67 ) % 0.93 ) % 2.25 % New Customized Reference Benchmark 3.76 ) % 1.26 ) % N/A Customized Reference Benchmark 3.92 ) % 1.31 ) % N/A |
| No Deduction of Taxes [Text Block] | Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. |
| Performance Table Market Index Changed [Text Block] | Beginning October 1, 2023, the Fund started to compare its performance to that of the Bloomberg Municipal Bond Index and the New Customized Reference Benchmark (commenced on September 30, 2016) |
| Material Change Date | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 3,922,952,604 |
| Holdings Count | Holding | 632 |
| Advisory Fees Paid, Amount | $ 20,372,144 |
| Investment Company Portfolio Turnover | 70% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Sector allocation Sector (a)(b) Percent of Utilities 21.9 % (c) County/City/Special District/School District 18.8 % (c) Transportation 14.9 % (c) State 12.9 % (c) Corporate 12.3 % (c) Health 6.7 % (c) Education 5.1 % (c) Housing 4.2 % (c) Tobacco 2.3 % (c) Industrial Conglomerates 0.9 % (c) Health Care Providers & Services — % (c) Credit quality allocation Credit Rating (a)(d) Percent of AAA/Aaa 14.4 % AA/Aa 44.5 % A 15.3 % BBB/Baa 3.7 % BB/Ba 2.4 % B 0.4 % N/R (e) 19.3 % (a) (b) (c) (d) (e) Excludes short-term securities. (a) (b) (c) (d) (e) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (a) (b) (c) (d) (e) Rounds to less than 0.1%. (a) (b) (c) (d) (e) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) (d) (e) The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after May 31, 2024 at blackrock.com/fundreports The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Material Fund Change Expenses [Text Block] | The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000038984 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Strategic Municipal Opportunities Fund |
| Class Name | Investor C Shares |
| Trading Symbol | MFMTX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Strategic Municipal Opportunities Fund (the “Fund”) for the period of June 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at blackrock.com/fundreports . |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | (800) 441‑7762 |
| Additional Information Website | blackrock.com/fundreports |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class name Costs of a $10,000 Costs paid as a percentage of a Investor C Shares $ 1.65 % |
| Expenses Paid, Amount | $ 167 |
| Expense Ratio, Percent | 1.65% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with the benefit of income augmented by a modest gain in prices. Declining inflation fueled expectations that the U.S. Federal Reserve was set to begin cutting interest rates in 2024, benefiting the broader fixed-income market. Municipal bonds were further helped by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. High-yield municipals performed particularly well in an environment of hearty investor risk appetites. What contributed to performance? The Fund’s use of U.S. Treasury futures to manage interest rate risk helped performance at a time in which Treasury yields rose (as prices fell). Overweight positions in AA rated securities and bonds with maturities of 20 years and longer contributed, as well. The Fund also benefited from keeping duration (interest-rate sensitivity) above that of the benchmark given the positive performance for the municipal market. Holdings in corporate-backed municipal issues, specifically pre-paid gas bonds, further contributed to results. The Fund’s use of derivatives marginally contributed to performance. What detracted from performance? A position in Puerto Rico Electric Power Authority bonds, which experienced a pronounced price decline early in the period, was a key detractor. An underweight in the healthcare sector also detracted, but to a lesser extent. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | Fund performance Cumulative performance: June 1, 2014 through May 31, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance. |
| Average Annual Return [Table Text Block] | Average annual total returns 1 Year 5 Years 10 Years Investor C Shares 2.84 % (0.71 ) % 1.34 % Investor C Shares (with sales charge) 1.84 % (0.71 ) % 1.34 % Bloomberg Municipal Bond Index 2.67 % 0.93 ) % 2.25 % New Customized Reference Benchmark 3.76 % 1.26 ) % N/A Customized Reference Benchmark 3.92 % 1.31 ) % N/A |
| No Deduction of Taxes [Text Block] | Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. |
| Performance Table Market Index Changed [Text Block] | Beginning October 1, 2023, the Fund started to compare its performance to that of the Bloomberg Municipal Bond Index and the New Customized Reference Benchmark (commenced on September 30, 2016) |
| Material Change Date | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 3,922,952,604 |
| Holdings Count | Holding | 632 |
| Advisory Fees Paid, Amount | $ 20,372,144 |
| Investment Company Portfolio Turnover | 70% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Sector allocation Sector (a)(b) Percent of Utilities 21.9 % (c) County/City/Special District/School District 18.8 % (c) Transportation 14.9 % (c) State 12.9 % (c) Corporate 12.3 % (c) Health 6.7 % (c) Education 5.1 % (c) Housing 4.2 % (c) Tobacco 2.3 % (c) Industrial Conglomerates 0.9 % (c) Health Care Providers & Services — % (c) Credit quality allocation Credit Rating (a)(d) Percent of AAA/Aaa 14.4 % AA/Aa 44.5 % A 15.3 % BBB/Baa 3.7 % BB/Ba 2.4 % B 0.4 % N/R (e) 19.3 % (a) (b) (c) (d) (e) Excludes short-term securities. (a) (b) (c) (d) (e) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (a) (b) (c) (d) (e) Rounds to less than 0.1%. (a) (b) (c) (d) (e) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) (d) (e) The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after May 31, 2024 at blackrock.com/fundreports The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Material Fund Change Expenses [Text Block] | The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000199785 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Strategic Municipal Opportunities Fund |
| Class Name | Class K Shares |
| Trading Symbol | MKMTX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Strategic Municipal Opportunities Fund (the “Fund”) for the period of June 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at blackrock.com/fundreports . |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | (800) 441‑7762 |
| Additional Information Website | blackrock.com/fundreports |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class name Costs of a $10,000 Costs paid as a percentage of a Class K Shares $ 0.58 % |
| Expenses Paid, Amount | $ 59 |
| Expense Ratio, Percent | 0.58% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with the benefit of income augmented by a modest gain in prices. Declining inflation fueled expectations that the U.S. Federal Reserve was set to begin cutting interest rates in 2024, benefiting the broader fixed-income market. Municipal bonds were further helped by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. High-yield municipals performed particularly well in an environment of hearty investor risk appetites. What contributed to performance? The Fund’s use of U.S. Treasury futures to manage interest rate risk helped performance at a time in which Treasury yields rose (as prices fell). Overweight positions in AA rated securities and bonds with maturities of 20 years and longer contributed, as well. The Fund also benefited from keeping duration (interest-rate sensitivity) above that of the benchmark given the positive performance for the municipal market. Holdings in corporate-backed municipal issues, specifically pre-paid gas bonds, further contributed to results. The Fund’s use of derivatives marginally contributed to performance. What detracted from performance? A position in Puerto Rico Electric Power Authority bonds, which experienced a pronounced price decline early in the period, was a key detractor. An underweight in the healthcare sector also detracted, but to a lesser extent. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | Fund performance Cumulative performance: June 1, 2014 through May 31, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance. |
| Average Annual Return [Table Text Block] | Average annual total returns 1 Year 5 Years 10 Years Class K Shares 3.94 % 0.34 % 2.24 % Bloomberg Municipal Bond Index 2.67 % 0.93 % 2.25 % New Customized Reference Benchmark 3.76 % 1.26 % N/A Customized Reference Benchmark 3.92 % 1.31 % N/A |
| No Deduction of Taxes [Text Block] | Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. |
| Performance Table Market Index Changed [Text Block] | Beginning October 1, 2023, the Fund started to compare its performance to that of the Bloomberg Municipal Bond Index and the New Customized Reference Benchmark (commenced on September 30, 2016) |
| Material Change Date | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 3,922,952,604 |
| Holdings Count | Holding | 632 |
| Advisory Fees Paid, Amount | $ 20,372,144 |
| Investment Company Portfolio Turnover | 70% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Sector allocation Sector (a)(b) Percent of Utilities 21.9 % (c) County/City/Special District/School District 18.8 % (c) Transportation 14.9 % (c) State 12.9 % (c) Corporate 12.3 % (c) Health 6.7 % (c) Education 5.1 % (c) Housing 4.2 % (c) Tobacco 2.3 % (c) Industrial Conglomerates 0.9 % (c) Health Care Providers & Services — % (c) Credit quality allocation Credit Rating (a)(d) Percent of AAA/Aaa 14.4 % AA/Aa 44.5 % A 15.3 % BBB/Baa 3.7 % BB/Ba 2.4 % B 0.4 % N/R (e) 19.3 % (a) (b) (c) (d) (e) Excludes short-term securities. (a) (b) (c) (d) (e) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (a) (b) (c) (d) (e) Rounds to less than 0.1%. (a) (b) (c) (d) (e) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) (d) (e) The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after May 31, 2024 at blackrock.com/fundreports The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Material Fund Change Expenses [Text Block] | The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000011339 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Strategic Municipal Opportunities Fund |
| Class Name | Investor A1 Shares |
| Trading Symbol | MDMTX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Strategic Municipal Opportunities Fund (the “Fund”) for the period of June 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at blackrock.com/fundreports . |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | (800) 441‑7762 |
| Additional Information Website | blackrock.com/fundreports |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class name Costs of a $10,000 Costs paid as a percentage of a Investor A1 Shares $ 0.73 % |
| Expenses Paid, Amount | $ 74 |
| Expense Ratio, Percent | 0.73% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with the benefit of income augmented by a modest gain in prices. Declining inflation fueled expectations that the U.S. Federal Reserve was set to begin cutting interest rates in 2024, benefiting the broader fixed-income market. Municipal bonds were further helped by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. High-yield municipals performed particularly well in an environment of hearty investor risk appetites. What contributed to performance? The Fund’s use of U.S. Treasury futures to manage interest rate risk helped performance at a time in which Treasury yields rose (as prices fell). Overweight positions in AA rated securities and bonds with maturities of 20 years and longer contributed, as well. The Fund also benefited from keeping duration (interest-rate sensitivity) above that of the benchmark given the positive performance for the municipal market. Holdings in corporate-backed municipal issues, specifically pre-paid gas bonds, further contributed to results. The Fund’s use of derivatives marginally contributed to performance. What detracted from performance? A position in Puerto Rico Electric Power Authority bonds, which experienced a pronounced price decline early in the period, was a key detractor. An underweight in the healthcare sector also detracted, but to a lesser extent. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | Fund performance Cumulative performance: June 1, 2014 through May 31, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance. |
| Average Annual Return [Table Text Block] | Average annual total returns 1 Year 5 Years 10 Years Investor A1 Shares 3.88 % 0.20 % 2.12 % Bloomberg Municipal Bond Index 2.67 % 0.93 % 2.25 % New Customized Reference Benchmark 3.76 % 1.26 % N/A Customized Reference Benchmark 3.92 % 1.31 % N/A |
| No Deduction of Taxes [Text Block] | Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. |
| Performance Table Market Index Changed [Text Block] | Beginning October 1, 2023, the Fund started to compare its performance to that of the Bloomberg Municipal Bond Index and the New Customized Reference Benchmark (commenced on September 30, 2016) |
| Material Change Date | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 3,922,952,604 |
| Holdings Count | Holding | 632 |
| Advisory Fees Paid, Amount | $ 20,372,144 |
| Investment Company Portfolio Turnover | 70% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Sector allocation Sector (a)(b) Percent of Utilities 21.9 % (c) County/City/Special District/School District 18.8 % (c) Transportation 14.9 % (c) State 12.9 % (c) Corporate 12.3 % (c) Health 6.7 % (c) Education 5.1 % (c) Housing 4.2 % (c) Tobacco 2.3 % (c) Industrial Conglomerates 0.9 % (c) Health Care Providers & Services — % (c) Credit quality allocation Credit Rating (a)(d) Percent of AAA/Aaa 14.4 % AA/Aa 44.5 % A 15.3 % BBB/Baa 3.7 % BB/Ba 2.4 % B 0.4 % N/R (e) 19.3 % (a) (b) (c) (d) (e) Excludes short-term securities. (a) (b) (c) (d) (e) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (a) (b) (c) (d) (e) Rounds to less than 0.1%. (a) (b) (c) (d) (e) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) (d) (e) The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after May 31, 2024 at blackrock.com/fundreports The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Material Fund Change Expenses [Text Block] | The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| C000011342 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Strategic Municipal Opportunities Fund |
| Class Name | Institutional Shares |
| Trading Symbol | MAMTX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Strategic Municipal Opportunities Fund (the “Fund”) for the period of June 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at blackrock.com/fundreports . |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | (800) 441‑7762 |
| Additional Information Website | blackrock.com/fundreports |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Class name Costs of a $10,000 Costs paid as a percentage of a Institutional Shares $ 0.66 % |
| Expenses Paid, Amount | $ 67 |
| Expense Ratio, Percent | 0.66% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with the benefit of income augmented by a modest gain in prices. Declining inflation fueled expectations that the U.S. Federal Reserve was set to begin cutting interest rates in 2024, benefiting the broader fixed-income market. Municipal bonds were further helped by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. High-yield municipals performed particularly well in an environment of hearty investor risk appetites. What contributed to performance? The Fund’s use of U.S. Treasury futures to manage interest rate risk helped performance at a time in which Treasury yields rose (as prices fell). Overweight positions in AA rated securities and bonds with maturities of 20 years and longer contributed, as well. The Fund also benefited from keeping duration (interest-rate sensitivity) above that of the benchmark given the positive performance for the municipal market. Holdings in corporate-backed municipal issues, specifically pre-paid gas bonds, further contributed to results. The Fund’s use of derivatives marginally contributed to performance. What detracted from performance? A position in Puerto Rico Electric Power Authority bonds, which experienced a pronounced price decline early in the period, was a key detractor. An underweight in the healthcare sector also detracted, but to a lesser extent. The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results. |
| Performance Past Does Not Indicate Future [Text] | Past performance is not an indication of future results. |
| Line Graph [Table Text Block] | Fund performance Cumulative performance: June 1, 2014 through May 31, 2024 Initial investment of $10,000 See “Average annual total returns” for additional information on fund performance. |
| Average Annual Return [Table Text Block] | Average annual total returns 1 Year 5 Years 10 Years Institutional Shares 3.85 % 0.27 % 2.19 % Bloomberg Municipal Bond Index 2.67 % 0.93 % 2.25 % New Customized Reference Benchmark 3.76 % 1.26 % N/A Customized Reference Benchmark 3.92 % 1.31 % N/A |
| No Deduction of Taxes [Text Block] | Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. |
| Performance Table Market Index Changed [Text Block] | Beginning October 1, 2023, the Fund started to compare its performance to that of the Bloomberg Municipal Bond Index and the New Customized Reference Benchmark (commenced on September 30, 2016) |
| Material Change Date | May 31, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 3,922,952,604 |
| Holdings Count | Holding | 632 |
| Advisory Fees Paid, Amount | $ 20,372,144 |
| Investment Company Portfolio Turnover | 70% |
| Additional Fund Statistics [Text Block] | Key Fund statistics Net Assets $ % Number of Portfolio Holdings $ % Net Investment Advisory Fees $ % Portfolio Turnover Rate $ % |
| Holdings [Text Block] | What did the Fund invest in? (as of May 31, 2024) Sector allocation Sector (a)(b) Percent of Utilities 21.9 % (c) County/City/Special District/School District 18.8 % (c) Transportation 14.9 % (c) State 12.9 % (c) Corporate 12.3 % (c) Health 6.7 % (c) Education 5.1 % (c) Housing 4.2 % (c) Tobacco 2.3 % (c) Industrial Conglomerates 0.9 % (c) Health Care Providers & Services — % (c) Credit quality allocation Credit Rating (a)(d) Percent of AAA/Aaa 14.4 % AA/Aa 44.5 % A 15.3 % BBB/Baa 3.7 % BB/Ba 2.4 % B 0.4 % N/R (e) 19.3 % (a) (b) (c) (d) (e) Excludes short-term securities. (a) (b) (c) (d) (e) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (a) (b) (c) (d) (e) Rounds to less than 0.1%. (a) (b) (c) (d) (e) For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. (a) (b) (c) (d) (e) The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Quality Explanation [Text Block] | The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. |
| Credit Ratings Selection [Text Block] | For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. |
| Material Fund Change [Text Block] | Material Fund changes This is a summary of certain changes to the Fund since May 31, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after May 31, 2024 at blackrock.com/fundreports The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Material Fund Change Expenses [Text Block] | The net expense ratio decreased from the prior fiscal year end primarily due to a decrease in expenses related to financing activities. |
| Updated Prospectus Phone Number | (800) 441-7762 |
| Updated Prospectus Web Address | blackrock.com/fundreports |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | |||||||||
| May 31, 2024 | May 31, 2024 | May 31, 2024 | May 31, 2023 | May 31, 2022 | May 31, 2021 | May 31, 2020 | May 31, 2019 | May 31, 2018 | May 31, 2017 | May 31, 2016 | May 31, 2015 | |
| C000038983 [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Investor A Shares (with sales charge) | |||||||||||
| Account Value | $ 11,631 | $ 11,631 | $ 11,631 | $ 11,222 | $ 11,455 | $ 12,379 | $ 11,069 | $ 11,602 | $ 11,138 | $ 10,683 | $ 10,491 | $ 9,748 |
| Average Annual Return, Percent | (0.76%) | (0.82%) | 1.52% | |||||||||
| C000038983 [Member] | Without Sales Load [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Investor A Shares | |||||||||||
| Average Annual Return, Percent | 3.64% | 0.05% | 1.96% | |||||||||
| C000038984 [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Investor C Shares (with sales charge) | |||||||||||
| Account Value | $ 11,438 | $ 11,438 | $ 11,438 | 11,026 | 11,255 | 12,267 | 11,044 | 11,673 | 11,291 | 10,904 | 10,790 | 10,103 |
| Average Annual Return, Percent | 1.84% | (0.71%) | 1.34% | |||||||||
| C000038984 [Member] | Without Sales Load [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Investor C Shares | |||||||||||
| Average Annual Return, Percent | 2.84% | (0.71%) | 1.34% | |||||||||
| C000199785 [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Class K Shares | |||||||||||
| Account Value | $ 12,481 | $ 12,481 | $ 12,481 | 12,008 | 12,210 | 13,168 | 11,733 | 12,272 | 11,746 | 11,231 | 11,006 | 10,213 |
| Average Annual Return, Percent | 3.94% | 0.34% | 2.24% | |||||||||
| C000011339 [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Investor A1 Shares | |||||||||||
| Account Value | $ 12,334 | $ 12,334 | $ 12,334 | 11,873 | 12,103 | 13,060 | 11,662 | 12,214 | 11,707 | 11,204 | 10,987 | 10,194 |
| Average Annual Return, Percent | 3.88% | 0.20% | 2.12% | |||||||||
| C000011342 [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Institutional Shares | |||||||||||
| Account Value | $ 12,425 | $ 12,425 | $ 12,425 | 11,964 | 12,176 | 13,141 | 11,715 | 12,261 | 11,743 | 11,231 | 11,006 | 10,213 |
| Average Annual Return, Percent | 3.85% | 0.27% | 2.19% | |||||||||
| Bloomberg Municipal Bond Index [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal Bond Index | |||||||||||
| Account Value | $ 12,488 | $ 12,488 | $ 12,488 | $ 12,163 | $ 12,104 | $ 12,986 | $ 12,399 | $ 11,925 | $ 11,207 | $ 11,083 | $ 10,924 | $ 10,318 |
| Average Annual Return, Percent | 2.67% | 0.93% | 2.25% | |||||||||
| Customized Reference Benchmark [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | Customized Reference Benchmark | |||||||||||
| Average Annual Return, Percent | 3.92% | 1.31% | ||||||||||
| New Customized Reference Benchmark [Member] | ||||||||||||
| Account Value [Line Items] | ||||||||||||
| Line Graph and Table Measure Name | New Customized Reference Benchmark | |||||||||||
| Average Annual Return, Percent | 3.76% | 1.26% |
| Shareholder Report, Holdings (Details) | May 31, 2024 | |
| C000038983 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.30% | [1],[2],[3] |
| C000038983 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | [1],[4] |
| C000038983 [Member] | Tabacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | [1],[4] |
| C000038983 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.90% | [1],[4] |
| C000038983 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.90% | [1],[4] |
| C000038983 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.30% | [1],[4] |
| C000038983 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [1],[4] |
| C000038983 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | [1],[4] |
| C000038983 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | [1],[4] |
| C000038983 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18.80% | [1],[4] |
| C000038983 [Member] | Health Care Providers And Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | [1],[4],[5] | |
| C000038983 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | [1],[4] |
| C000038984 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.30% | [6],[7],[8] |
| C000038984 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | [6],[9] |
| C000038984 [Member] | Tabacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | [6],[9] |
| C000038984 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.90% | [6],[9] |
| C000038984 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.90% | [6],[9] |
| C000038984 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.30% | [6],[9] |
| C000038984 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [6],[9] |
| C000038984 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | [6],[9] |
| C000038984 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | [6],[9] |
| C000038984 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18.80% | [6],[9] |
| C000038984 [Member] | Health Care Providers And Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | [6],[9],[10] | |
| C000038984 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | [6],[9] |
| C000199785 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.30% | [11],[12],[13] |
| C000199785 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | [11],[14] |
| C000199785 [Member] | Tabacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | [11],[14] |
| C000199785 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.90% | [11],[14] |
| C000199785 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.90% | [11],[14] |
| C000199785 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.30% | [11],[14] |
| C000199785 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [11],[14] |
| C000199785 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | [11],[14] |
| C000199785 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | [11],[14] |
| C000199785 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18.80% | [11],[14] |
| C000199785 [Member] | Health Care Providers And Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | [11],[14],[15] | |
| C000199785 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | [11],[14] |
| C000011339 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.30% | [16],[17],[18] |
| C000011339 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | [16],[19] |
| C000011339 [Member] | Tabacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | [16],[19] |
| C000011339 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.90% | [16],[19] |
| C000011339 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.90% | [16],[19] |
| C000011339 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.30% | [16],[19] |
| C000011339 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [16],[19] |
| C000011339 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | [16],[19] |
| C000011339 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | [16],[19] |
| C000011339 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18.80% | [16],[19] |
| C000011339 [Member] | Health Care Providers And Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | [16],[19],[20] | |
| C000011339 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | [16],[19] |
| C000011342 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.30% | [21],[22],[23] |
| C000011342 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.10% | [21],[24] |
| C000011342 [Member] | Tabacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.30% | [21],[24] |
| C000011342 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.90% | [21],[24] |
| C000011342 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 21.90% | [21],[24] |
| C000011342 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.30% | [21],[24] |
| C000011342 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [21],[24] |
| C000011342 [Member] | Industrial Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.90% | [21],[24] |
| C000011342 [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 6.70% | [21],[24] |
| C000011342 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18.80% | [21],[24] |
| C000011342 [Member] | Health Care Providers And Services [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | [21],[24],[25] | |
| C000011342 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.20% | [21],[24] |
| [1]Excludes short-term securities.[2]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[3]The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[4]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[5]Rounds to less than 0.1%.[6]Excludes short-term securities.[7]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[8]The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[9]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[10]Rounds to less than 0.1%.[11]Excludes short-term securities.[12]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[13]The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[14]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[15]Rounds to less than 0.1%.[16]Excludes short-term securities.[17]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[18]The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[19]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[20]Rounds to less than 0.1%.[21]Excludes short-term securities.[22]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[23]The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors and individual investments. Using this approach, the investment adviser has deemed certain of these unrated securities as investment grade quality. As of May 31, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[24]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[25]Rounds to less than 0.1%. | ||
| Label | Element | Value | |
| C000038983 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.40% | [1],[2] |
| C000038983 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 14.40% | [1],[2] |
| C000038983 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.70% | [1],[2] |
| C000038983 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 44.50% | [1],[2] |
| C000038983 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.40% | [1],[2] |
| C000038983 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 15.30% | [1],[2] |
| C000011339 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.40% | [3],[4] |
| C000011339 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 14.40% | [3],[4] |
| C000011339 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.70% | [3],[4] |
| C000011339 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 44.50% | [3],[4] |
| C000011339 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.40% | [3],[4] |
| C000011339 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 15.30% | [3],[4] |
| C000011342 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.40% | [5],[6] |
| C000011342 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 14.40% | [5],[6] |
| C000011342 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.70% | [5],[6] |
| C000011342 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 44.50% | [5],[6] |
| C000011342 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.40% | [5],[6] |
| C000011342 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 15.30% | [5],[6] |
| C000199785 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.40% | [7],[8] |
| C000199785 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 14.40% | [7],[8] |
| C000199785 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.70% | [7],[8] |
| C000199785 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 44.50% | [7],[8] |
| C000199785 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.40% | [7],[8] |
| C000199785 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 15.30% | [7],[8] |
| C000038984 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.40% | [9],[10] |
| C000038984 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 14.40% | [9],[10] |
| C000038984 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 3.70% | [9],[10] |
| C000038984 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 44.50% | [9],[10] |
| C000038984 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.40% | [9],[10] |
| C000038984 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 15.30% | [9],[10] |
| [1]Excludes short-term securities.[2]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[3]Excludes short-term securities.[4]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[5]Excludes short-term securities.[6]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[7]Excludes short-term securities.[8]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.[9]Excludes short-term securities.[10]For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change. | |||
