INTRODUCTION AND BASIS OF PRESENTATION - Narrative (Details) - Blackrock Inc - Customer Concentration Risk	9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025
Revenue from Contract with Customer, Product and Service Benchmark
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	11.80%	10.60%
Revenue from Contract with Customer, Segment Benchmark \| Index
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	19.80%	18.50%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.