Shareholder Report
|
6 Months Ended |
|
Dec. 31, 2025
USD ($)
Holding
|
|---|
| Shareholder Report [Line Items] |
|
|
| Document Type |
N-CSRS
|
|
| Amendment Flag |
false
|
|
| Registrant Name |
BlackRock Municipal Bond Fund, Inc.
|
|
| Entity Central Index Key |
0000225635
|
|
| Entity Investment Company Type |
N-1A
|
|
| Document Period End Date |
Dec. 31, 2025
|
|
| 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 semi-annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Class K Shares |
$22 |
0.43%(a) |
|
|
| Expenses Paid, Amount |
$ 22
|
|
| Expense Ratio, Percent |
0.43%
|
[1] |
| Net Assets |
$ 5,785,534,294
|
|
| Holdings Count | Holding |
460
|
|
| Investment Company Portfolio Turnover |
37.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$5,785,534,294 |
| Number of Portfolio Holdings |
460 |
| Portfolio Turnover Rate |
37% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
25.0 |
% |
| Corporate |
17.2 |
% |
| State |
13.8 |
% |
| Utilities |
12.0 |
% |
| Health |
11.1 |
% |
| County/City/Special District/School District |
9.0 |
% |
| Housing |
4.7 |
% |
| Education |
3.6 |
% |
| Tobacco |
1.4 |
% |
| Fixed Income Funds |
1.3 |
% |
| Other* |
0.9 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
12.5 |
% |
| AA/Aa |
57.3 |
% |
| A |
19.9 |
% |
| BBB/Baa |
4.4 |
% |
| BB/Ba |
0.5 |
% |
| B |
0.2 |
% |
| N/R |
5.2 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
| * |
Ten largest sectors are presented. Additional sectors are found in Other. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| 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 semi-annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Investor C Shares |
$76 |
1.48%(a) |
|
|
| Expenses Paid, Amount |
$ 76
|
|
| Expense Ratio, Percent |
1.48%
|
[2] |
| Net Assets |
$ 5,785,534,294
|
|
| Holdings Count | Holding |
460
|
|
| Investment Company Portfolio Turnover |
37.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$5,785,534,294 |
| Number of Portfolio Holdings |
460 |
| Portfolio Turnover Rate |
37% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
25.0 |
% |
| Corporate |
17.2 |
% |
| State |
13.8 |
% |
| Utilities |
12.0 |
% |
| Health |
11.1 |
% |
| County/City/Special District/School District |
9.0 |
% |
| Housing |
4.7 |
% |
| Education |
3.6 |
% |
| Tobacco |
1.4 |
% |
| Fixed Income Funds |
1.3 |
% |
| Other* |
0.9 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
12.5 |
% |
| AA/Aa |
57.3 |
% |
| A |
19.9 |
% |
| BBB/Baa |
4.4 |
% |
| BB/Ba |
0.5 |
% |
| B |
0.2 |
% |
| N/R |
5.2 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
| * |
Ten largest sectors are presented. Additional sectors are found in Other. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| 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 semi-annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Investor A Shares |
$37 |
0.73%(a) |
|
|
| Expenses Paid, Amount |
$ 37
|
|
| Expense Ratio, Percent |
0.73%
|
[3] |
| Net Assets |
$ 5,785,534,294
|
|
| Holdings Count | Holding |
460
|
|
| Investment Company Portfolio Turnover |
37.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$5,785,534,294 |
| Number of Portfolio Holdings |
460 |
| Portfolio Turnover Rate |
37% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
25.0 |
% |
| Corporate |
17.2 |
% |
| State |
13.8 |
% |
| Utilities |
12.0 |
% |
| Health |
11.1 |
% |
| County/City/Special District/School District |
9.0 |
% |
| Housing |
4.7 |
% |
| Education |
3.6 |
% |
| Tobacco |
1.4 |
% |
| Fixed Income Funds |
1.3 |
% |
| Other* |
0.9 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
12.5 |
% |
| AA/Aa |
57.3 |
% |
| A |
19.9 |
% |
| BBB/Baa |
4.4 |
% |
| BB/Ba |
0.5 |
% |
| B |
0.2 |
% |
| N/R |
5.2 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
| * |
Ten largest sectors are presented. Additional sectors are found in Other. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| 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 semi-annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Service Shares |
$37 |
0.73%(a) |
|
|
| Expenses Paid, Amount |
$ 37
|
|
| Expense Ratio, Percent |
0.73%
|
[4] |
| Net Assets |
$ 5,785,534,294
|
|
| Holdings Count | Holding |
460
|
|
| Investment Company Portfolio Turnover |
37.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$5,785,534,294 |
| Number of Portfolio Holdings |
460 |
| Portfolio Turnover Rate |
37% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
25.0 |
% |
| Corporate |
17.2 |
% |
| State |
13.8 |
% |
| Utilities |
12.0 |
% |
| Health |
11.1 |
% |
| County/City/Special District/School District |
9.0 |
% |
| Housing |
4.7 |
% |
| Education |
3.6 |
% |
| Tobacco |
1.4 |
% |
| Fixed Income Funds |
1.3 |
% |
| Other* |
0.9 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
12.5 |
% |
| AA/Aa |
57.3 |
% |
| A |
19.9 |
% |
| BBB/Baa |
4.4 |
% |
| BB/Ba |
0.5 |
% |
| B |
0.2 |
% |
| N/R |
5.2 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
| * |
Ten largest sectors are presented. Additional sectors are found in Other. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| 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 semi-annual shareholder report contains important information about BlackRock National Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Institutional Shares |
$25 |
0.48%(a) |
|
|
| Expenses Paid, Amount |
$ 25
|
|
| Expense Ratio, Percent |
0.48%
|
[5] |
| Net Assets |
$ 5,785,534,294
|
|
| Holdings Count | Holding |
460
|
|
| Investment Company Portfolio Turnover |
37.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$5,785,534,294 |
| Number of Portfolio Holdings |
460 |
| Portfolio Turnover Rate |
37% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
25.0 |
% |
| Corporate |
17.2 |
% |
| State |
13.8 |
% |
| Utilities |
12.0 |
% |
| Health |
11.1 |
% |
| County/City/Special District/School District |
9.0 |
% |
| Housing |
4.7 |
% |
| Education |
3.6 |
% |
| Tobacco |
1.4 |
% |
| Fixed Income Funds |
1.3 |
% |
| Other* |
0.9 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
12.5 |
% |
| AA/Aa |
57.3 |
% |
| A |
19.9 |
% |
| BBB/Baa |
4.4 |
% |
| BB/Ba |
0.5 |
% |
| B |
0.2 |
% |
| N/R |
5.2 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
| * |
Ten largest sectors are presented. Additional sectors are found in Other. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| C000006125 [Member] |
|
|
| Shareholder Report [Line Items] |
|
|
| Fund Name |
BlackRock Short Duration Muni Fund
|
|
| Class Name |
Institutional Shares
|
|
| Trading Symbol |
MALMX
|
|
| Annual or Semi-Annual Statement [Text Block] |
This semi-annual shareholder report contains important information about BlackRock Short Duration Muni Fund (the “Fund”) (formerly known as BlackRock Short-Term Municipal Fund) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Institutional Shares |
$18 |
0.36%(a) |
|
|
| Expenses Paid, Amount |
$ 18
|
|
| Expense Ratio, Percent |
0.36%
|
[6] |
| Net Assets |
$ 488,622,879
|
|
| Holdings Count | Holding |
186
|
|
| Investment Company Portfolio Turnover |
24.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$488,622,879 |
| Number of Portfolio Holdings |
186 |
| Portfolio Turnover Rate |
24% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
26.9 |
% |
| Corporate |
25.6 |
% |
| Health |
18.8 |
% |
| Housing |
9.3 |
% |
| County/City/Special District/School District |
5.9 |
% |
| Utilities |
5.3 |
% |
| State |
5.2 |
% |
| Education |
2.3 |
% |
| Tobacco |
0.7 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
6.1 |
% |
| AA/Aa |
43.0 |
% |
| A |
39.1 |
% |
| BBB/Baa |
8.2 |
% |
| BB/Ba |
0.6 |
% |
| N/R |
3.0 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| C000038034 [Member] |
|
|
| Shareholder Report [Line Items] |
|
|
| Fund Name |
BlackRock Short Duration Muni Fund
|
|
| Class Name |
Investor A Shares
|
|
| Trading Symbol |
MELMX
|
|
| Annual or Semi-Annual Statement [Text Block] |
This semi-annual shareholder report contains important information about BlackRock Short Duration Muni Fund (the “Fund”) (formerly known as BlackRock Short-Term Municipal Fund) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Investor A Shares |
$31 |
0.60%(a) |
|
|
| Expenses Paid, Amount |
$ 31
|
|
| Expense Ratio, Percent |
0.60%
|
[7] |
| Net Assets |
$ 488,622,879
|
|
| Holdings Count | Holding |
186
|
|
| Investment Company Portfolio Turnover |
24.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$488,622,879 |
| Number of Portfolio Holdings |
186 |
| Portfolio Turnover Rate |
24% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
26.9 |
% |
| Corporate |
25.6 |
% |
| Health |
18.8 |
% |
| Housing |
9.3 |
% |
| County/City/Special District/School District |
5.9 |
% |
| Utilities |
5.3 |
% |
| State |
5.2 |
% |
| Education |
2.3 |
% |
| Tobacco |
0.7 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
6.1 |
% |
| AA/Aa |
43.0 |
% |
| A |
39.1 |
% |
| BBB/Baa |
8.2 |
% |
| BB/Ba |
0.6 |
% |
| N/R |
3.0 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| C000006122 [Member] |
|
|
| Shareholder Report [Line Items] |
|
|
| Fund Name |
BlackRock Short Duration Muni Fund
|
|
| Class Name |
Investor A1 Shares
|
|
| Trading Symbol |
MDLMX
|
|
| Annual or Semi-Annual Statement [Text Block] |
This semi-annual shareholder report contains important information about BlackRock Short Duration Muni Fund (the “Fund”) (formerly known as BlackRock Short-Term Municipal Fund) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Investor A1 Shares |
$24 |
0.46%(a) |
|
|
| Expenses Paid, Amount |
$ 24
|
|
| Expense Ratio, Percent |
0.46%
|
[8] |
| Net Assets |
$ 488,622,879
|
|
| Holdings Count | Holding |
186
|
|
| Investment Company Portfolio Turnover |
24.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$488,622,879 |
| Number of Portfolio Holdings |
186 |
| Portfolio Turnover Rate |
24% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
26.9 |
% |
| Corporate |
25.6 |
% |
| Health |
18.8 |
% |
| Housing |
9.3 |
% |
| County/City/Special District/School District |
5.9 |
% |
| Utilities |
5.3 |
% |
| State |
5.2 |
% |
| Education |
2.3 |
% |
| Tobacco |
0.7 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
6.1 |
% |
| AA/Aa |
43.0 |
% |
| A |
39.1 |
% |
| BBB/Baa |
8.2 |
% |
| BB/Ba |
0.6 |
% |
| N/R |
3.0 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| C000006124 [Member] |
|
|
| Shareholder Report [Line Items] |
|
|
| Fund Name |
BlackRock Short Duration Muni Fund
|
|
| Class Name |
Investor C Shares
|
|
| Trading Symbol |
MFLMX
|
|
| Annual or Semi-Annual Statement [Text Block] |
This semi-annual shareholder report contains important information about BlackRock Short Duration Muni Fund (the “Fund”) (formerly known as BlackRock Short-Term Municipal Fund) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Investor C Shares |
$69 |
1.36%(a) |
|
|
| Expenses Paid, Amount |
$ 69
|
|
| Expense Ratio, Percent |
1.36%
|
[9] |
| Net Assets |
$ 488,622,879
|
|
| Holdings Count | Holding |
186
|
|
| Investment Company Portfolio Turnover |
24.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$488,622,879 |
| Number of Portfolio Holdings |
186 |
| Portfolio Turnover Rate |
24% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
26.9 |
% |
| Corporate |
25.6 |
% |
| Health |
18.8 |
% |
| Housing |
9.3 |
% |
| County/City/Special District/School District |
5.9 |
% |
| Utilities |
5.3 |
% |
| State |
5.2 |
% |
| Education |
2.3 |
% |
| Tobacco |
0.7 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
6.1 |
% |
| AA/Aa |
43.0 |
% |
| A |
39.1 |
% |
| BBB/Baa |
8.2 |
% |
| BB/Ba |
0.6 |
% |
| N/R |
3.0 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
| C000038035 [Member] |
|
|
| Shareholder Report [Line Items] |
|
|
| Fund Name |
BlackRock Short Duration Muni Fund
|
|
| Class Name |
Class K Shares
|
|
| Trading Symbol |
MPLMX
|
|
| Annual or Semi-Annual Statement [Text Block] |
This semi-annual shareholder report contains important information about BlackRock Short Duration Muni Fund (the “Fund”) (formerly known as BlackRock Short-Term Municipal Fund) for the period of July 1, 2025 to December 31, 2025.
|
|
| Shareholder Report Annual or Semi-Annual |
semi-annual shareholder report
|
|
| Additional Information [Text Block] |
You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.
|
|
| Additional Information Phone Number |
(800) 441‑7762
|
|
| Additional Information Website |
blackrock.com/fundreports
|
|
| Expenses [Text Block] |
What were the Fund costs for the last six months ? (based on a hypothetical $10,000 investment)
| Class name |
Costs of a $10,000
investment |
Costs paid as a percentage of a
$10,000 investment |
| Class K Shares |
$16 |
0.31%(a) |
|
|
| Expenses Paid, Amount |
$ 16
|
|
| Expense Ratio, Percent |
0.31%
|
[10] |
| Net Assets |
$ 488,622,879
|
|
| Holdings Count | Holding |
186
|
|
| Investment Company Portfolio Turnover |
24.00%
|
|
| Additional Fund Statistics [Text Block] |
| Key Fund statistics |
|
| Net Assets |
$488,622,879 |
| Number of Portfolio Holdings |
186 |
| Portfolio Turnover Rate |
24% |
|
|
| Holdings [Text Block] |
What did the Fund invest in? (as of December 31, 2025)
| Sector allocation |
| Sector(a) |
Percent of Total
Investments(b) |
|
| Transportation |
26.9 |
% |
| Corporate |
25.6 |
% |
| Health |
18.8 |
% |
| Housing |
9.3 |
% |
| County/City/Special District/School District |
5.9 |
% |
| Utilities |
5.3 |
% |
| State |
5.2 |
% |
| Education |
2.3 |
% |
| Tobacco |
0.7 |
% |
| Credit quality allocation |
| Credit Rating(c) |
Percent of Total
Investments(b) |
|
| AAA/Aaa |
6.1 |
% |
| AA/Aa |
43.0 |
% |
| A |
39.1 |
% |
| BBB/Baa |
8.2 |
% |
| BB/Ba |
0.6 |
% |
| N/R |
3.0 |
% |
| (a) |
For purposes of this report, sector sub-classifications may differ from those utilized by the Fund 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. |
|
|
| Credit Quality Explanation [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.
|
|
| 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.
|
|
|
|