Investor A C and Institutional [Member] Expense Example - Investor A, C and Institutional - BlackRock National Municipal Fund |
Jun. 30, 2026
USD ($)
|
|---|---|
| Investor A Shares | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 498 |
| Expense Example, with Redemption, 3 Years | 665 |
| Expense Example, with Redemption, 5 Years | 846 |
| Expense Example, with Redemption, 10 Years | 1,368 |
| Institutional Shares | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 51 |
| Expense Example, with Redemption, 3 Years | 176 |
| Expense Example, with Redemption, 5 Years | 311 |
| Expense Example, with Redemption, 10 Years | 707 |
| Investor C Shares | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 253 |
| Expense Example, with Redemption, 3 Years | 487 |
| Expense Example, with Redemption, 5 Years | 844 |
| Expense Example, with Redemption, 10 Years | $ 1,647 |