Class K [Member] Investment Objectives and Goals - Class K - BlackRock Short Duration Muni Fund |
Jun. 30, 2026 |
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| Prospectus [Line Items] | |
| Risk/Return [Heading] | Fund Overview Key Facts About BlackRock Short Duration Muni Fund |
| Objective [Heading] | Investment Objective |
| Objective, Primary [Text Block] | The investment objective of BlackRock Short Duration Muni Fund (formerly, BlackRock Short-Term Municipal Fund) (the “Short Duration Fund” or the “Fund”) is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.
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