Class K [Member] Investment Objectives and Goals - Class K - iShares Municipal Bond Index Fund |
Dec. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Risk/Return [Heading] | Fund Overview Key Facts About iShares Municipal Bond Index Fund |
| Objective [Heading] | Investment Objective |
| Objective, Primary [Text Block] | The investment objective of iShares Municipal Bond Index Fund (the “Fund”), a series of BlackRock FundsSM (the “Trust”), is to seek to provide investment results that correspond to the total return performance of fixed-income securities in the aggregate, as represented by the ICE BofA US Municipal Securities Index (the “Underlying Index”).
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