| Form N-CSR Cover | 12 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Municipal Bond Fund, Inc. |
| Entity Central Index Key | 0000225635 |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 12 Months Ended |
| Jun. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BlackRock Municipal Bond Fund, Inc. |
| Entity Central Index Key | 0000225635 |
| Document Period End Date | Jun. 30, 2024 |
| C000032428 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock High Yield Municipal Fund |
| Class Name | Institutional Shares |
| Trading Symbol | MAYHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock High Yield Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 $ 0.57 % |
| Expenses Paid, Amount | $ 60 |
| Expense Ratio, Percent | 0.57% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? High-yield municipal bonds gained ground during the reporting period, with price appreciation augmenting the contribution from income. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Longer-duration securities with maturities of 20 years and longer made the largest contribution, with a significant portion of the positive return coming from bonds having maturities of 25 years and above. (Duration is a measure of interest rate sensitivity). In terms of credit tiers, the strongest absolute returns came from not rated and BB rated bonds, respectively. Other industries and tax-backed states were the top contributors at the sector level. Among individual securities, Puerto Rico Commonwealth contingent value instruments and Port Beaumont Navigation District of Jefferson County, TX were the top performing bonds. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, certain individual securities lost ground due to issuer-specific developments. For instance, the bonds of the industrial wood-pellet supplier Enviva, Inc. slid in price after the issuer filed for Chapter 11 bankruptcy. In addition, the bonds of Puerto Rico Electric Power Authority declined as bankruptcy hearing proceedings continued to cloud the outcome for bondholder recovery. 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: July 1, 2014 through June 30, 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 9.64 % 2.28 % 4.12 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal High Yield Bond Index 8.90 % 3.00 % 4.66 % High Yield Customized Reference Benchmark 7.06 % 2.43 % 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. |
| Material Change Date | Jun. 30, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 1,644,901,083 |
| Holdings Count | Holding | 700 |
| Advisory Fees Paid, Amount | $ 7,095,681 |
| Investment Company Portfolio Turnover | 34% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) State 19.4 % Corporate 16.1 % Transportation 13.1 % Education 12.9 % Health 12.6 % County/City/Special District/School District 11.1 % Utilities 5.2 % Housing 4.8 % Tobacco 4.0 % Other * 0.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 0.3 % AA/Aa 11.7 % A 10.5 % BBB/Baa 8.8 % BB/Ba 9.4 % B 1.9 % N/R (d) 57.4 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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 June 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after June 30, 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 |
| C000032425 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock High Yield Municipal Fund |
| Class Name | Investor A Shares |
| Trading Symbol | MDYHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock High Yield Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.82 % |
| Expenses Paid, Amount | $ 86 |
| Expense Ratio, Percent | 0.82% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? High-yield municipal bonds gained ground during the reporting period, with price appreciation augmenting the contribution from income. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Longer-duration securities with maturities of 20 years and longer made the largest contribution, with a significant portion of the positive return coming from bonds having maturities of 25 years and above. (Duration is a measure of interest rate sensitivity). In terms of credit tiers, the strongest absolute returns came from not rated and BB rated bonds, respectively. Other industries and tax-backed states were the top contributors at the sector level. Among individual securities, Puerto Rico Commonwealth contingent value instruments and Port Beaumont Navigation District of Jefferson County, TX were the top performing bonds. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, certain individual securities lost ground due to issuer-specific developments. For instance, the bonds of the industrial wood-pellet supplier Enviva, Inc. slid in price after the issuer filed for Chapter 11 bankruptcy. In addition, the bonds of Puerto Rico Electric Power Authority declined as bankruptcy hearing proceedings continued to cloud the outcome for bondholder recovery. 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: July 1, 2014 through June 30, 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 9.38 % 2.03 % 3.86 % Investor A Shares (with sales charge) 4.73 % 1.14 % 3.41 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal High Yield Bond Index 8.90 % 3.00 % 4.66 % High Yield Customized Reference Benchmark 7.06 % 2.43 % 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 1,644,901,083 |
| Holdings Count | Holding | 700 |
| Advisory Fees Paid, Amount | $ 7,095,681 |
| Investment Company Portfolio Turnover | 34% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) State 19.4 % Corporate 16.1 % Transportation 13.1 % Education 12.9 % Health 12.6 % County/City/Special District/School District 11.1 % Utilities 5.2 % Housing 4.8 % Tobacco 4.0 % Other * 0.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 0.3 % AA/Aa 11.7 % A 10.5 % BBB/Baa 8.8 % BB/Ba 9.4 % B 1.9 % N/R (d) 57.4 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000032427 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock High Yield Municipal Fund |
| Class Name | Investor C Shares |
| Trading Symbol | MCYHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock High Yield Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 1.57 % |
| Expenses Paid, Amount | $ 164 |
| Expense Ratio, Percent | 1.57% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? High-yield municipal bonds gained ground during the reporting period, with price appreciation augmenting the contribution from income. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Longer-duration securities with maturities of 20 years and longer made the largest contribution, with a significant portion of the positive return coming from bonds having maturities of 25 years and above. (Duration is a measure of interest rate sensitivity). In terms of credit tiers, the strongest absolute returns came from not rated and BB rated bonds, respectively. Other industries and tax-backed states were the top contributors at the sector level. Among individual securities, Puerto Rico Commonwealth contingent value instruments and Port Beaumont Navigation District of Jefferson County, TX were the top performing bonds. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, certain individual securities lost ground due to issuer-specific developments. For instance, the bonds of the industrial wood-pellet supplier Enviva, Inc. slid in price after the issuer filed for Chapter 11 bankruptcy. In addition, the bonds of Puerto Rico Electric Power Authority declined as bankruptcy hearing proceedings continued to cloud the outcome for bondholder recovery. 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: July 1, 2014 through June 30, 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 8.67 % 1.29 % 3.25 % Investor C Shares (with sales charge) 7.67 % 1.29 % 3.25 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal High Yield Bond Index 8.90 % 3.00 % 4.66 % High Yield Customized Reference Benchmark 7.06 % 2.43 % 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 1,644,901,083 |
| Holdings Count | Holding | 700 |
| Advisory Fees Paid, Amount | $ 7,095,681 |
| Investment Company Portfolio Turnover | 34% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) State 19.4 % Corporate 16.1 % Transportation 13.1 % Education 12.9 % Health 12.6 % County/City/Special District/School District 11.1 % Utilities 5.2 % Housing 4.8 % Tobacco 4.0 % Other * 0.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 0.3 % AA/Aa 11.7 % A 10.5 % BBB/Baa 8.8 % BB/Ba 9.4 % B 1.9 % N/R (d) 57.4 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000199786 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock High Yield Municipal Fund |
| Class Name | Class K Shares |
| Trading Symbol | MKYHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock High Yield Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 $ 0.52 % |
| Expenses Paid, Amount | $ 55 |
| Expense Ratio, Percent | 0.52% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? High-yield municipal bonds gained ground during the reporting period, with price appreciation augmenting the contribution from income. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Longer-duration securities with maturities of 20 years and longer made the largest contribution, with a significant portion of the positive return coming from bonds having maturities of 25 years and above. (Duration is a measure of interest rate sensitivity). In terms of credit tiers, the strongest absolute returns came from not rated and BB rated bonds, respectively. Other industries and tax-backed states were the top contributors at the sector level. Among individual securities, Puerto Rico Commonwealth contingent value instruments and Port Beaumont Navigation District of Jefferson County, TX were the top performing bonds. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, certain individual securities lost ground due to issuer-specific developments. For instance, the bonds of the industrial wood-pellet supplier Enviva, Inc. slid in price after the issuer filed for Chapter 11 bankruptcy. In addition, the bonds of Puerto Rico Electric Power Authority declined as bankruptcy hearing proceedings continued to cloud the outcome for bondholder recovery. 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: July 1, 2014 through June 30, 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 9.70 % 2.33 % 4.15 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal High Yield Bond Index 8.90 % 3.00 % 4.66 % High Yield Customized Reference Benchmark 7.06 % 2.43 % 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. |
| Material Change Date | Jun. 30, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 1,644,901,083 |
| Holdings Count | Holding | 700 |
| Advisory Fees Paid, Amount | $ 7,095,681 |
| Investment Company Portfolio Turnover | 34% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) State 19.4 % Corporate 16.1 % Transportation 13.1 % Education 12.9 % Health 12.6 % County/City/Special District/School District 11.1 % Utilities 5.2 % Housing 4.8 % Tobacco 4.0 % Other * 0.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 0.3 % AA/Aa 11.7 % A 10.5 % BBB/Baa 8.8 % BB/Ba 9.4 % B 1.9 % N/R (d) 57.4 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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 June 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after June 30, 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 |
| C000006121 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock National Municipal Fund |
| Class Name | Institutional Shares |
| Trading Symbol | MANLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.50 % |
| Expenses Paid, Amount | $ 51 |
| Expense Ratio, Percent | 0.50% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with income playing the largest role in total returns. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Holdings in longer-duration securities (those with above-average interest rate sensitivity) performed well during the reporting period. At the sector level, corporate-backed securities (primarily pre-paid gas) provided the largest absolute returns, followed by transportation, tax-backed states, and utilities. In terms of credit tiers, AA and A rated securities were the strongest performers. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive performance for the broader market, few aspects of the Fund’s positioning detracted from absolute returns. With that said, there were a few BB and non-rated securities that became distressed during the reporting period. For example, the bonds of Michigan Finance Authority for Explore Academy—a charter school—fell sharply after the issuer deferred its interest payments. 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: July 1, 2014 through June 30, 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 3.62 % 0.86 % 2.21 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % |
| 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 7,420,334,025 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 31,854,084 |
| Investment Company Portfolio Turnover | 58% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Transportation 22.9 % State 18.0 % Corporate 16.3 % Utilities 10.8 % County/City/Special District/School District 9.4 % Health 9.2 % Education 9.2 % Housing 3.7 % Tobacco 0.4 % Other * 0.1 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 12.5 % AA/Aa 53.9 % A 24.6 % BBB/Baa 2.6 % BB/Ba 1.5 % B 0.1 % N/R (d) 4.8 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000100249 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock National Municipal Fund |
| Class Name | Service Shares |
| Trading Symbol | BNMSX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 Service Shares $ 0.75 % |
| Expenses Paid, Amount | $ 76 |
| Expense Ratio, Percent | 0.75% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with income playing the largest role in total returns. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Holdings in longer-duration securities (those with above-average interest rate sensitivity) performed well during the reporting period. At the sector level, corporate-backed securities (primarily pre-paid gas) provided the largest absolute returns, followed by transportation, tax-backed states, and utilities. In terms of credit tiers, AA and A rated securities were the strongest performers. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive performance for the broader market, few aspects of the Fund’s positioning detracted from absolute returns. With that said, there were a few BB and non-rated securities that became distressed during the reporting period. For example, the bonds of Michigan Finance Authority for Explore Academy—a charter school—fell sharply after the issuer deferred its interest payments. 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: July 1, 2014 through June 30, 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 Service Shares 3.36 % 0.61 % 1.98 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % |
| 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 7,420,334,025 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 31,854,084 |
| Investment Company Portfolio Turnover | 58% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Transportation 22.9 % State 18.0 % Corporate 16.3 % Utilities 10.8 % County/City/Special District/School District 9.4 % Health 9.2 % Education 9.2 % Housing 3.7 % Tobacco 0.4 % Other * 0.1 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 12.5 % AA/Aa 53.9 % A 24.6 % BBB/Baa 2.6 % BB/Ba 1.5 % B 0.1 % N/R (d) 4.8 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000006118 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock National Municipal Fund |
| Class Name | Investor A Shares |
| Trading Symbol | MDNLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.75 % |
| Expenses Paid, Amount | $ 76 |
| Expense Ratio, Percent | 0.75% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with income playing the largest role in total returns. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Holdings in longer-duration securities (those with above-average interest rate sensitivity) performed well during the reporting period. At the sector level, corporate-backed securities (primarily pre-paid gas) provided the largest absolute returns, followed by transportation, tax-backed states, and utilities. In terms of credit tiers, AA and A rated securities were the strongest performers. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive performance for the broader market, few aspects of the Fund’s positioning detracted from absolute returns. With that said, there were a few BB and non-rated securities that became distressed during the reporting period. For example, the bonds of Michigan Finance Authority for Explore Academy—a charter school—fell sharply after the issuer deferred its interest payments. 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: July 1, 2014 through June 30, 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 3.46 ) % 0.63 ) % 1.98 % Investor A Shares (with sales charge) (0.94 ) % (0.24 ) % 1.54 % Bloomberg Municipal Bond Index 3.21 ) % 1.16 ) % 2.39 % |
| 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 7,420,334,025 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 31,854,084 |
| Investment Company Portfolio Turnover | 58% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Transportation 22.9 % State 18.0 % Corporate 16.3 % Utilities 10.8 % County/City/Special District/School District 9.4 % Health 9.2 % Education 9.2 % Housing 3.7 % Tobacco 0.4 % Other * 0.1 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 12.5 % AA/Aa 53.9 % A 24.6 % BBB/Baa 2.6 % BB/Ba 1.5 % B 0.1 % N/R (d) 4.8 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000038033 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock National Municipal Fund |
| Class Name | Investor C Shares |
| Trading Symbol | MFNLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 1.50 % |
| Expenses Paid, Amount | $ 152 |
| Expense Ratio, Percent | 1.50% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with income playing the largest role in total returns. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Holdings in longer-duration securities (those with above-average interest rate sensitivity) performed well during the reporting period. At the sector level, corporate-backed securities (primarily pre-paid gas) provided the largest absolute returns, followed by transportation, tax-backed states, and utilities. In terms of credit tiers, AA and A rated securities were the strongest performers. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive performance for the broader market, few aspects of the Fund’s positioning detracted from absolute returns. With that said, there were a few BB and non-rated securities that became distressed during the reporting period. For example, the bonds of Michigan Finance Authority for Explore Academy—a charter school—fell sharply after the issuer deferred its interest payments. 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: July 1, 2014 through June 30, 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 2.59 % (0.12 ) % 1.39 % Investor C Shares (with sales charge) 1.59 % (0.12 ) % 1.39 % Bloomberg Municipal Bond Index 3.21 % 1.16 ) % 2.39 % |
| 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 7,420,334,025 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 31,854,084 |
| Investment Company Portfolio Turnover | 58% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Transportation 22.9 % State 18.0 % Corporate 16.3 % Utilities 10.8 % County/City/Special District/School District 9.4 % Health 9.2 % Education 9.2 % Housing 3.7 % Tobacco 0.4 % Other * 0.1 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 12.5 % AA/Aa 53.9 % A 24.6 % BBB/Baa 2.6 % BB/Ba 1.5 % B 0.1 % N/R (d) 4.8 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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. |
| C000100250 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock National Municipal Fund |
| Class Name | Class K Shares |
| Trading Symbol | BNMLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 $ 0.45 % |
| Expenses Paid, Amount | $ 46 |
| Expense Ratio, Percent | 0.45% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal bond market gained ground during the reporting period, with income playing the largest role in total returns. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Holdings in longer-duration securities (those with above-average interest rate sensitivity) performed well during the reporting period. At the sector level, corporate-backed securities (primarily pre-paid gas) provided the largest absolute returns, followed by transportation, tax-backed states, and utilities. In terms of credit tiers, AA and A rated securities were the strongest performers. The Fund’s cash position had no material effect on performance. What detracted from performance? At a time of positive performance for the broader market, few aspects of the Fund’s positioning detracted from absolute returns. With that said, there were a few BB and non-rated securities that became distressed during the reporting period. For example, the bonds of Michigan Finance Authority for Explore Academy—a charter school—fell sharply after the issuer deferred its interest payments. 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: July 1, 2014 through June 30, 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 3.67 % 0.91 % 2.27 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % |
| 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. |
| Material Change Date | Jun. 30, 2023 |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 7,420,334,025 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 31,854,084 |
| Investment Company Portfolio Turnover | 58% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Transportation 22.9 % State 18.0 % Corporate 16.3 % Utilities 10.8 % County/City/Special District/School District 9.4 % Health 9.2 % Education 9.2 % Housing 3.7 % Tobacco 0.4 % Other * 0.1 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 12.5 % AA/Aa 53.9 % A 24.6 % BBB/Baa 2.6 % BB/Ba 1.5 % B 0.1 % N/R (d) 4.8 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments. * Ten largest sectors are presented. Additional sectors are found in Other. |
| 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 June 30, 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 June 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available approximately 120 days after June 30, 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 |
| C000006125 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Short-Term Municipal Fund |
| Class Name | Institutional Shares |
| Trading Symbol | MALMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Short-Term Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.36 % |
| Expenses Paid, Amount | $ 37 |
| Expense Ratio, Percent | 0.36% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal broader bond market gained ground during the reporting period, with income playing the largest role in total returns. Short-term municipals lagged relative to the market as a whole. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Yield was the largest contributor to the Fund’s performance. Positions in lower-rated bonds provided strong absolute returns and outpaced the broader investment-grade market. Yield curve positioning also added value, as did the Fund’s allocation to cash. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, a few individual securities lost ground due to the timing of the purchases. 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: July 1, 2014 through June 30, 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 4.13 % 1.01 % 0.92 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal 1-5 Year Index 2.72 % 0.96 % 1.22 % New Short-Term Customized Reference Benchmark 2.87 % 1.10 % N/A Short-Term Customized Reference Benchmark 2.98 % 1.07 % 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. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 470,417,947 |
| Holdings Count | Holding | 171 |
| Advisory Fees Paid, Amount | $ 1,271,655 |
| Investment Company Portfolio Turnover | 90% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Corporate 31.2 % Health 14.6 % State 13.6 % County/City/Special District/School District 13.4 % Transportation 9.6 % Utilities 7.6 % Housing 5.2 % Education 4.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 4.6 % AA/Aa 30.1 % A 54.7 % BBB/Baa 8.4 % N/R (d) 2.2 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 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 June 30, 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. |
| C000038034 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Short-Term Municipal Fund |
| Class Name | Investor A Shares |
| Trading Symbol | MELMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Short-Term Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.60 % |
| Expenses Paid, Amount | $ 61 |
| Expense Ratio, Percent | 0.60% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal broader bond market gained ground during the reporting period, with income playing the largest role in total returns. Short-term municipals lagged relative to the market as a whole. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Yield was the largest contributor to the Fund’s performance. Positions in lower-rated bonds provided strong absolute returns and outpaced the broader investment-grade market. Yield curve positioning also added value, as did the Fund’s allocation to cash. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, a few individual securities lost ground due to the timing of the purchases. 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: July 1, 2014 through June 30, 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 3.88 % 0.79 % 0.68 % Investor A Shares (with sales charge) 0.77 % 0.17 % 0.37 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal 1-5 Year Index 2.72 % 0.96 % 1.22 % New Short-Term Customized Reference Benchmark 2.87 % 1.10 % N/A Short-Term Customized Reference Benchmark 2.98 % 1.07 % 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] | Effective November 1, 2023, the Fund has changed the benchmarks against which it measures its performance from the Short-Term Customized Reference Benchmark to the New Short-Term Customized Reference Benchmark. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 470,417,947 |
| Holdings Count | Holding | 171 |
| Advisory Fees Paid, Amount | $ 1,271,655 |
| Investment Company Portfolio Turnover | 90% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Corporate 31.2 % Health 14.6 % State 13.6 % County/City/Special District/School District 13.4 % Transportation 9.6 % Utilities 7.6 % Housing 5.2 % Education 4.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 4.6 % AA/Aa 30.1 % A 54.7 % BBB/Baa 8.4 % N/R (d) 2.2 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 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 June 30, 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. |
| C000006122 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Short-Term Municipal Fund |
| Class Name | Investor A1 Shares |
| Trading Symbol | MDLMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Short-Term Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.46 % |
| Expenses Paid, Amount | $ 47 |
| Expense Ratio, Percent | 0.46% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal broader bond market gained ground during the reporting period, with income playing the largest role in total returns. Short-term municipals lagged relative to the market as a whole. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Yield was the largest contributor to the Fund’s performance. Positions in lower-rated bonds provided strong absolute returns and outpaced the broader investment-grade market. Yield curve positioning also added value, as did the Fund’s allocation to cash. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, a few individual securities lost ground due to the timing of the purchases. 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: July 1, 2014 through June 30, 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 4.03 % 0.90 % 0.81 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal 1-5 Year Index 2.72 % 0.96 % 1.22 % New Short-Term Customized Reference Benchmark 2.87 % 1.10 % N/A Short-Term Customized Reference Benchmark 2.98 % 1.07 % 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] | Effective November 1, 2023, the Fund has changed the benchmarks against which it measures its performance from the Short-Term Customized Reference Benchmark to the New Short-Term Customized Reference Benchmark. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 470,417,947 |
| Holdings Count | Holding | 171 |
| Advisory Fees Paid, Amount | $ 1,271,655 |
| Investment Company Portfolio Turnover | 90% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Corporate 31.2 % Health 14.6 % State 13.6 % County/City/Special District/School District 13.4 % Transportation 9.6 % Utilities 7.6 % Housing 5.2 % Education 4.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 4.6 % AA/Aa 30.1 % A 54.7 % BBB/Baa 8.4 % N/R (d) 2.2 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 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 June 30, 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. |
| C000006124 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Short-Term Municipal Fund |
| Class Name | Investor C Shares |
| Trading Symbol | MFLMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Short-Term Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 1.36 % |
| Expenses Paid, Amount | $ 138 |
| Expense Ratio, Percent | 1.36% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal broader bond market gained ground during the reporting period, with income playing the largest role in total returns. Short-term municipals lagged relative to the market as a whole. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Yield was the largest contributor to the Fund’s performance. Positions in lower-rated bonds provided strong absolute returns and outpaced the broader investment-grade market. Yield curve positioning also added value, as did the Fund’s allocation to cash. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, a few individual securities lost ground due to the timing of the purchases. 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: July 1, 2014 through June 30, 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 3.01 % 0.00 % 0.05 % Investor C Shares (with sales charge) 2.01 % 0.00 % 0.05 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal 1-5 Year Index 2.72 % 0.96 % 1.22 % New Short-Term Customized Reference Benchmark 2.87 % 1.10 % N/A Short-Term Customized Reference Benchmark 2.98 % 1.07 % 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] | Effective November 1, 2023, the Fund has changed the benchmarks against which it measures its performance from the Short-Term Customized Reference Benchmark to the New Short-Term Customized Reference Benchmark. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 470,417,947 |
| Holdings Count | Holding | 171 |
| Advisory Fees Paid, Amount | $ 1,271,655 |
| Investment Company Portfolio Turnover | 90% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Corporate 31.2 % Health 14.6 % State 13.6 % County/City/Special District/School District 13.4 % Transportation 9.6 % Utilities 7.6 % Housing 5.2 % Education 4.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 4.6 % AA/Aa 30.1 % A 54.7 % BBB/Baa 8.4 % N/R (d) 2.2 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 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 June 30, 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. |
| C000038035 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | BlackRock Short-Term Municipal Fund |
| Class Name | Class K Shares |
| Trading Symbol | MPLMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about BlackRock Short-Term Municipal Fund (the “Fund”) for the period of July 1, 2023 to June 30, 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 |
| 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 $ 0.31 % |
| Expenses Paid, Amount | $ 32 |
| Expense Ratio, Percent | 0.31% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? The municipal broader bond market gained ground during the reporting period, with income playing the largest role in total returns. Short-term municipals lagged relative to the market as a whole. 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 from November 2023 onward. Municipal bonds were well supported by positive economic growth, strong issuer fundamentals, and favorable supply-and-demand trends. What contributed to performance? Yield was the largest contributor to the Fund’s performance. Positions in lower-rated bonds provided strong absolute returns and outpaced the broader investment-grade market. Yield curve positioning also added value, as did the Fund’s allocation to cash. What detracted from performance? At a time of positive returns for the broader market, few aspects of the Fund’s positioning detracted from absolute performance. With that said, a few individual securities lost ground due to the timing of the purchases. 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: July 1, 2014 through June 30, 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 4.08 % 1.06 % 0.96 % Bloomberg Municipal Bond Index 3.21 % 1.16 % 2.39 % Bloomberg Municipal 1-5 Year Index 2.72 % 0.96 % 1.22 % New Short-Term Customized Reference Benchmark 2.87 % 1.10 % N/A Short-Term Customized Reference Benchmark 2.98 % 1.07 % 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] | Effective November 1, 2023, the Fund has changed the benchmarks against which it measures its performance from the Short-Term Customized Reference Benchmark to the New Short-Term Customized Reference Benchmark. |
| Updated Performance Information Location [Text Block] | Visit blackrock.com |
| Net Assets | $ 470,417,947 |
| Holdings Count | Holding | 171 |
| Advisory Fees Paid, Amount | $ 1,271,655 |
| Investment Company Portfolio Turnover | 90% |
| 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 June 30, 2024) Sector allocation Sector (a) Percent of (b) Corporate 31.2 % Health 14.6 % State 13.6 % County/City/Special District/School District 13.4 % Transportation 9.6 % Utilities 7.6 % Housing 5.2 % Education 4.8 % Credit quality allocation Credit Rating (c) Percent of (b) AAA/Aaa 4.6 % AA/Aa 30.1 % A 54.7 % BBB/Baa 8.4 % N/R (d) 2.2 % (a) For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. (b) Excludes short-term securities. (c) 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. (d) 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 June 30, 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 June 30, 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. |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | ||||||||||
| Jun. 30, 2024 | Jun. 30, 2024 | Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2015 | Jun. 30, 2014 | |
| C000032428 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Institutional Shares | ||||||||||||
| Account Value | $ 14,976 | $ 14,976 | $ 14,976 | $ 13,660 | $ 13,538 | $ 15,533 | $ 13,391 | $ 13,377 | $ 12,460 | $ 11,892 | $ 11,936 | $ 10,627 | $ 10,000 |
| Average Annual Return, Percent | 9.64% | 2.28% | 4.12% | ||||||||||
| C000032425 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | 4.73% | 1.14% | 3.41% | ||||||||||
| C000032425 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares | ||||||||||||
| Account Value | $ 13,984 | $ 13,984 | $ 13,984 | 12,785 | 12,703 | 14,615 | 12,628 | 12,649 | 11,811 | 11,301 | 11,362 | 10,150 | 9,575 |
| Average Annual Return, Percent | 9.38% | 2.03% | 3.86% | ||||||||||
| C000032427 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | 7.67% | 1.29% | 3.25% | ||||||||||
| C000032427 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares | ||||||||||||
| Account Value | $ 13,766 | $ 13,766 | $ 13,766 | 12,586 | 12,505 | 14,490 | 12,619 | 12,721 | 11,969 | 11,551 | 11,698 | 10,520 | 10,000 |
| Average Annual Return, Percent | 8.67% | 1.29% | 3.25% | ||||||||||
| C000199786 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Class K Shares | ||||||||||||
| Account Value | $ 15,018 | $ 15,018 | $ 15,018 | 13,707 | 13,562 | 15,553 | 13,402 | 13,384 | 12,462 | 11,892 | 11,936 | 10,627 | 10,000 |
| Average Annual Return, Percent | 9.70% | 2.33% | 4.15% | ||||||||||
| C000006121 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Institutional Shares | ||||||||||||
| Account Value | $ 12,440 | $ 12,440 | $ 12,440 | 12,006 | 11,626 | 12,902 | 12,219 | 11,919 | 11,268 | 11,023 | 11,023 | 10,333 | 10,000 |
| Average Annual Return, Percent | 3.62% | 0.86% | 2.21% | ||||||||||
| C000100249 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Service Shares | ||||||||||||
| Account Value | $ 12,166 | $ 12,166 | $ 12,166 | 11,771 | 11,427 | 12,712 | 12,080 | 11,800 | 11,183 | 10,965 | 10,991 | 10,323 | 10,000 |
| Average Annual Return, Percent | 3.36% | 0.61% | 1.98% | ||||||||||
| C000006118 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | (0.94%) | (0.24%) | 1.54% | ||||||||||
| C000006118 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares | ||||||||||||
| Account Value | $ 11,654 | $ 11,654 | $ 11,654 | 11,264 | 10,935 | 12,165 | 11,561 | 11,295 | 10,715 | 10,498 | 10,521 | 9,887 | 9,575 |
| Average Annual Return, Percent | 3.46% | 0.63% | 1.98% | ||||||||||
| C000038033 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | 1.59% | (0.12%) | 1.39% | ||||||||||
| C000038033 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares | ||||||||||||
| Account Value | $ 11,476 | $ 11,476 | $ 11,476 | 11,103 | 10,769 | 12,069 | 11,546 | 11,364 | 10,862 | 10,731 | 10,825 | 10,248 | 10,000 |
| Average Annual Return, Percent | 2.59% | (0.12%) | 1.39% | ||||||||||
| C000100250 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Class K Shares | ||||||||||||
| Account Value | $ 12,517 | $ 12,517 | $ 12,517 | 12,074 | 11,687 | 12,962 | 12,281 | 11,963 | 11,304 | 11,052 | 11,046 | 10,352 | 10,000 |
| Average Annual Return, Percent | 3.67% | 0.91% | 2.27% | ||||||||||
| C000006125 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Institutional Shares | ||||||||||||
| Account Value | $ 10,956 | $ 10,956 | $ 10,956 | 10,522 | 10,344 | 10,670 | 10,575 | 10,422 | 10,185 | 10,114 | 10,104 | 9,989 | 10,000 |
| Average Annual Return, Percent | 4.13% | 1.01% | 0.92% | ||||||||||
| C000038034 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | 0.77% | 0.17% | 0.37% | ||||||||||
| C000038034 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A Shares | ||||||||||||
| Account Value | $ 10,378 | $ 10,378 | $ 10,378 | 9,990 | 9,844 | 10,178 | 10,111 | 9,979 | 9,775 | 9,740 | 9,745 | 9,672 | 9,700 |
| Average Annual Return, Percent | 3.88% | 0.79% | 0.68% | ||||||||||
| C000006122 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor A1 Shares | ||||||||||||
| Account Value | $ 10,843 | $ 10,843 | $ 10,843 | 10,424 | 10,258 | 10,592 | 10,508 | 10,366 | 10,141 | 10,079 | 10,080 | 9,977 | 10,000 |
| Average Annual Return, Percent | 4.03% | 0.90% | 0.81% | ||||||||||
| C000006124 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares (with sales charge) | ||||||||||||
| Average Annual Return, Percent | 2.01% | 0% | 0.05% | ||||||||||
| C000006124 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Investor C Shares | ||||||||||||
| Account Value | $ 10,050 | $ 10,050 | $ 10,050 | 9,674 | 9,533 | 9,935 | 9,946 | 9,900 | 9,770 | 9,806 | 9,891 | 9,881 | 10,000 |
| Average Annual Return, Percent | 3.01% | 0% | 0.05% | ||||||||||
| C000038035 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Class K Shares | ||||||||||||
| Account Value | $ 11,007 | $ 11,007 | $ 11,007 | 10,576 | 10,381 | 10,703 | 10,603 | 10,444 | 10,202 | 10,125 | 10,112 | 9,999 | 10,000 |
| Average Annual Return, Percent | 4.08% | 1.06% | 0.96% | ||||||||||
| Bloomberg Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal Bond Index | ||||||||||||
| Account Value | $ 12,669 | $ 12,669 | $ 12,669 | 12,274 | 11,895 | 13,010 | 12,490 | 11,958 | 11,207 | 11,034 | 11,088 | 10,300 | 10,000 |
| Average Annual Return, Percent | 3.21% | 1.16% | 2.39% | ||||||||||
| Bloomberg Municipal High Yield Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal High Yield Bond Index | ||||||||||||
| Account Value | $ 15,772 | $ 15,772 | $ 15,772 | 14,483 | 14,081 | 15,716 | 13,746 | 13,606 | 12,623 | 11,782 | 11,640 | 10,384 | 10,000 |
| Average Annual Return, Percent | 8.90% | 3% | 4.66% | ||||||||||
| High Yield Customized Reference Benchmark [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | High Yield Customized Reference Benchmark | ||||||||||||
| Average Annual Return, Percent | 7.06% | 2.43% | |||||||||||
| Bloomberg Municipal 1 5 Year Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal 1-5 Year Index | ||||||||||||
| Account Value | $ 11,285 | $ 11,285 | $ 11,285 | $ 10,986 | $ 10,868 | $ 11,230 | $ 11,078 | $ 10,760 | $ 10,398 | $ 10,335 | $ 10,287 | $ 10,066 | $ 10,000 |
| Average Annual Return, Percent | 2.72% | 0.96% | 1.22% | ||||||||||
| New Short Term Customized Reference Benchmark [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | New Short-Term Customized Reference Benchmark | ||||||||||||
| Average Annual Return, Percent | 2.87% | 1.10% | |||||||||||
| Short Term Customized Reference Benchmark [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Short-Term Customized Reference Benchmark | ||||||||||||
| Average Annual Return, Percent | 2.98% | 1.07% |
| Shareholder Report, Holdings (Details) | Jun. 30, 2024 | |
| C000032428 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.40% | [1],[2],[3] |
| C000032428 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.10% | [1],[4] |
| C000032428 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.80% | [1],[4],[5] |
| C000032428 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [1],[4] |
| C000032428 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.40% | [1],[4] |
| C000032428 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.10% | [1],[4] |
| C000032428 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [1],[4] |
| C000032428 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.60% | [1],[4] |
| C000032428 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | [1],[4] |
| C000032428 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.10% | [1],[4] |
| C000032428 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [1],[4] |
| C000032425 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.40% | [6],[7],[8] |
| C000032425 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.10% | [6],[9] |
| C000032425 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.80% | [6],[9],[10] |
| C000032425 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [6],[9] |
| C000032425 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.40% | [6],[9] |
| C000032425 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.10% | [6],[9] |
| C000032425 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [6],[9] |
| C000032425 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.60% | [6],[9] |
| C000032425 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | [6],[9] |
| C000032425 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.10% | [6],[9] |
| C000032425 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [6],[9] |
| C000032427 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.40% | [11],[12],[13] |
| C000032427 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.10% | [11],[14] |
| C000032427 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.80% | [11],[14],[15] |
| C000032427 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [11],[14] |
| C000032427 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.40% | [11],[14] |
| C000032427 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.10% | [11],[14] |
| C000032427 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [11],[14] |
| C000032427 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.60% | [11],[14] |
| C000032427 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | [11],[14] |
| C000032427 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.10% | [11],[14] |
| C000032427 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [11],[14] |
| C000199786 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 57.40% | [16],[17],[18] |
| C000199786 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.10% | [16],[19] |
| C000199786 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.80% | [16],[19],[20] |
| C000199786 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [16],[19] |
| C000199786 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 19.40% | [16],[19] |
| C000199786 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 11.10% | [16],[19] |
| C000199786 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [16],[19] |
| C000199786 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.60% | [16],[19] |
| C000199786 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4% | [16],[19] |
| C000199786 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.10% | [16],[19] |
| C000199786 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 12.90% | [16],[19] |
| C000006121 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [21],[22],[23] |
| C000006121 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 22.90% | [21],[24] |
| C000006121 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | [21],[24],[25] |
| C000006121 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.80% | [21],[24] |
| C000006121 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | [21],[24] |
| C000006121 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.40% | [21],[24] |
| C000006121 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | [21],[24] |
| C000006121 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [21],[24] |
| C000006121 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | [21],[24] |
| C000006121 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | [21],[24] |
| C000006121 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [21],[24] |
| C000100249 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [26],[27],[28] |
| C000100249 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 22.90% | [26],[29] |
| C000100249 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | [26],[29],[30] |
| C000100249 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.80% | [26],[29] |
| C000100249 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | [26],[29] |
| C000100249 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.40% | [26],[29] |
| C000100249 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | [26],[29] |
| C000100249 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [26],[29] |
| C000100249 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | [26],[29] |
| C000100249 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | [26],[29] |
| C000100249 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [26],[29] |
| C000006118 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [31],[32],[33] |
| C000006118 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 22.90% | [31],[34] |
| C000006118 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | [31],[34],[35] |
| C000006118 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.80% | [31],[34] |
| C000006118 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | [31],[34] |
| C000006118 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.40% | [31],[34] |
| C000006118 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | [31],[34] |
| C000006118 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [31],[34] |
| C000006118 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | [31],[34] |
| C000006118 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | [31],[34] |
| C000006118 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [31],[34] |
| C000038033 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [36],[37],[38] |
| C000038033 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 22.90% | [36],[39] |
| C000038033 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | [36],[39],[40] |
| C000038033 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.80% | [36],[39] |
| C000038033 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | [36],[39] |
| C000038033 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.40% | [36],[39] |
| C000038033 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | [36],[39] |
| C000038033 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [36],[39] |
| C000038033 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | [36],[39] |
| C000038033 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | [36],[39] |
| C000038033 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [36],[39] |
| C000100250 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [41],[42],[43] |
| C000100250 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 22.90% | [41],[44] |
| C000100250 [Member] | Unclassified Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.10% | [41],[44],[45] |
| C000100250 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 10.80% | [41],[44] |
| C000100250 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 18% | [41],[44] |
| C000100250 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.40% | [41],[44] |
| C000100250 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 3.70% | [41],[44] |
| C000100250 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [41],[44] |
| C000100250 [Member] | Tobacco [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 0.40% | [41],[44] |
| C000100250 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 16.30% | [41],[44] |
| C000100250 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.20% | [41],[44] |
| C000006125 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | [46],[47],[48] |
| C000006125 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.60% | [46],[49] |
| C000006125 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | [46],[49] |
| C000006125 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.60% | [46],[49] |
| C000006125 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | [46],[49] |
| C000006125 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [46],[49] |
| C000006125 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.60% | [46],[49] |
| C000006125 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | [46],[49] |
| C000006125 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [46],[49] |
| C000038034 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | [50],[51],[52] |
| C000038034 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.60% | [50],[53] |
| C000038034 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | [50],[53] |
| C000038034 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.60% | [50],[53] |
| C000038034 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | [50],[53] |
| C000038034 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [50],[53] |
| C000038034 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.60% | [50],[53] |
| C000038034 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | [50],[53] |
| C000038034 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [50],[53] |
| C000006122 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | [54],[55],[56] |
| C000006122 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.60% | [54],[57] |
| C000006122 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | [54],[57] |
| C000006122 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.60% | [54],[57] |
| C000006122 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | [54],[57] |
| C000006122 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [54],[57] |
| C000006122 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.60% | [54],[57] |
| C000006122 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | [54],[57] |
| C000006122 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [54],[57] |
| C000006124 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | [58],[59],[60] |
| C000006124 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.60% | [58],[61] |
| C000006124 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | [58],[61] |
| C000006124 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.60% | [58],[61] |
| C000006124 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | [58],[61] |
| C000006124 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [58],[61] |
| C000006124 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.60% | [58],[61] |
| C000006124 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | [58],[61] |
| C000006124 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [58],[61] |
| C000038035 [Member] | N R [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 2.20% | [62],[63],[64] |
| C000038035 [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 9.60% | [62],[65] |
| C000038035 [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 7.60% | [62],[65] |
| C000038035 [Member] | State [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.60% | [62],[65] |
| C000038035 [Member] | County City Special District School District [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 13.40% | [62],[65] |
| C000038035 [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 5.20% | [62],[65] |
| C000038035 [Member] | Health [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 14.60% | [62],[65] |
| C000038035 [Member] | Corporate Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 31.20% | [62],[65] |
| C000038035 [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Total Investments | 4.80% | [62],[65] |
| [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 June 30, 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]Ten largest sectors are presented. Additional sectors are found in Other.[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 June 30, 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]Ten largest sectors are presented. Additional sectors are found in Other.[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 June 30, 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]Ten largest sectors are presented. Additional sectors are found in Other.[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 June 30, 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]Ten largest sectors are presented. Additional sectors are found in Other.[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 June 30, 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]Ten largest sectors are presented. Additional sectors are found in Other.[26]Excludes short-term securities.[27]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.[28]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[29]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[30]Ten largest sectors are presented. Additional sectors are found in Other.[31]Excludes short-term securities.[32]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.[33]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[34]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[35]Ten largest sectors are presented. Additional sectors are found in Other.[36]Excludes short-term securities.[37]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.[38]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[39]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[40]Ten largest sectors are presented. Additional sectors are found in Other.[41]Excludes short-term securities.[42]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.[43]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[44]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[45]Ten largest sectors are presented. Additional sectors are found in Other.[46]Excludes short-term securities.[47]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.[48]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[49]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[50]Excludes short-term securities.[51]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.[52]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[53]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[54]Excludes short-term securities.[55]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.[56]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[57]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[58]Excludes short-term securities.[59]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.[60]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[61]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes.[62]Excludes short-term securities.[63]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.[64]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 June 30, 2024, the market value of unrated securities deemed by the investment adviser to be investment grade represents less than 1.0% of total investments.[65]For purposes of this report, sector sub-classifications may differ from those utilized for compliance purposes. | ||
| Label | Element | Value | |
| C000038035 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 30.10% | [1],[2] |
| C000038035 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 54.70% | [1],[2] |
| C000038035 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.40% | [1],[2] |
| C000038035 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 4.60% | [1],[2] |
| C000100250 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.50% | [3],[4] |
| C000100250 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 53.90% | [3],[4] |
| C000100250 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 24.60% | [3],[4] |
| C000100250 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.10% | [3],[4] |
| C000100250 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.60% | [3],[4] |
| C000100250 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 12.50% | [3],[4] |
| C000006125 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 30.10% | [5],[6] |
| C000006125 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 54.70% | [5],[6] |
| C000006125 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.40% | [5],[6] |
| C000006125 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 4.60% | [5],[6] |
| C000006124 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 30.10% | [7],[8] |
| C000006124 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 54.70% | [7],[8] |
| C000006124 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.40% | [7],[8] |
| C000006124 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 4.60% | [7],[8] |
| C000038033 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.50% | [9],[10] |
| C000038033 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 53.90% | [9],[10] |
| C000038033 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 24.60% | [9],[10] |
| C000038033 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.10% | [9],[10] |
| C000038033 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.60% | [9],[10] |
| C000038033 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 12.50% | [9],[10] |
| C000038034 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 30.10% | [11],[12] |
| C000038034 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 54.70% | [11],[12] |
| C000038034 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.40% | [11],[12] |
| C000038034 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 4.60% | [11],[12] |
| C000032425 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 9.40% | [13],[14] |
| C000032425 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 11.70% | [13],[14] |
| C000032425 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 10.50% | [13],[14] |
| C000032425 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.90% | [13],[14] |
| C000032425 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.80% | [13],[14] |
| C000032425 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [13],[14] |
| C000006121 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.50% | [15],[16] |
| C000006121 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 53.90% | [15],[16] |
| C000006121 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 24.60% | [15],[16] |
| C000006121 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.10% | [15],[16] |
| C000006121 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.60% | [15],[16] |
| C000006121 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 12.50% | [15],[16] |
| C000006122 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 30.10% | [17],[18] |
| C000006122 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 54.70% | [17],[18] |
| C000006122 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.40% | [17],[18] |
| C000006122 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 4.60% | [17],[18] |
| C000006118 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.50% | [19],[20] |
| C000006118 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 53.90% | [19],[20] |
| C000006118 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 24.60% | [19],[20] |
| C000006118 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.10% | [19],[20] |
| C000006118 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.60% | [19],[20] |
| C000006118 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 12.50% | [19],[20] |
| C000032427 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 9.40% | [21],[22] |
| C000032427 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 11.70% | [21],[22] |
| C000032427 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 10.50% | [21],[22] |
| C000032427 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.90% | [21],[22] |
| C000032427 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.80% | [21],[22] |
| C000032427 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [21],[22] |
| C000199786 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 9.40% | [23],[24] |
| C000199786 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 11.70% | [23],[24] |
| C000199786 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 10.50% | [23],[24] |
| C000199786 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.90% | [23],[24] |
| C000199786 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.80% | [23],[24] |
| C000199786 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [23],[24] |
| C000100249 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.50% | [25],[26] |
| C000100249 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 53.90% | [25],[26] |
| C000100249 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 24.60% | [25],[26] |
| C000100249 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.10% | [25],[26] |
| C000100249 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 2.60% | [25],[26] |
| C000100249 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 12.50% | [25],[26] |
| C000032428 [Member] | Standard & Poor's, BB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 9.40% | [27],[28] |
| C000032428 [Member] | Standard & Poor's, AA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 11.70% | [27],[28] |
| C000032428 [Member] | Standard & Poor's, A Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 10.50% | [27],[28] |
| C000032428 [Member] | Standard & Poor's, B Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 1.90% | [27],[28] |
| C000032428 [Member] | Standard & Poor's, BBB Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 8.80% | [27],[28] |
| C000032428 [Member] | Standard & Poor's, AAA Rating [Member] | |||
| Percent of Total Investments | oef_PctOfTotalInv | 0.30% | [27],[28] |
| [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.[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]Excludes short-term securities.[14]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.[15]Excludes short-term securities.[16]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.[17]Excludes short-term securities.[18]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.[19]Excludes short-term securities.[20]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.[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]Excludes short-term securities.[24]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.[25]Excludes short-term securities.[26]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.[27]Excludes short-term securities.[28]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. | |||
