Class K [Member] Investment Objectives and Goals - Class K - iShares Russell 1000 Large-Cap Index Fund |
Dec. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Risk/Return [Heading] | Fund Overview Key Facts About iShares Russell 1000 Large-Cap Index Fund |
| Objective [Heading] | Investment Objective |
| Objective, Primary [Text Block] | The investment objective of iShares Russell 1000 Large-Cap Index Fund (“Large-Cap Index Fund” or the “Fund”), a series of BlackRock Funds III (the “Trust”), is to match the performance of the Russell 1000® Index (the “Russell 1000” or the “Underlying Index”) as closely as possible before the deduction of Fund expenses.
|