Service Shares [Member] Expense Example - Service Shares - BlackRock National Municipal Fund - Service Shares	Jun. 30, 2026 USD ($)
Prospectus [Line Items]
Expense Example, with Redemption, 1 Year	$ 77
Expense Example, with Redemption, 3 Years	263
Expense Example, with Redemption, 5 Years	466
Expense Example, with Redemption, 10 Years	$ 1,051

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