v3.26.1
Class K [Member] Investment Objectives and Goals - Class K - iShares Russell 2000 Small-Cap Index Fund
Dec. 31, 2025
Prospectus [Line Items]  
Risk/Return [Heading] Fund Overview Key Facts About iShares Russell 2000 Small-Cap Index Fund
Objective [Heading] Investment Objective
Objective, Primary [Text Block]
The investment objective of iShares Russell 2000 Small-Cap Index Fund (“Russell 2000 Small-Cap Index Fund”or the “Fund”), a series of BlackRock Index Funds, Inc. (the “Corporation”), is to match the performance of the Russell 2000® Index (the “Russell 2000” or the Underlying Index) as closely as possible before the deduction of Fund expenses.