Variable Interest Entities Reflects adoption of ASU 2015-12 - Balances Relating to Variable Interest Entities in which BlackRock is Not Primary Beneficiary (Detail) - Variable Interest Entity, Not Primary Beneficiary [Member] - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Investments [Member]
Variable Interest Entity [Line Items]
Sponsored investment products	$ 2,290	$ 2,377
Advisory Fee Receivables [Member]
Variable Interest Entity [Line Items]
Sponsored investment products	141	116
Other Net Assets (Liabilities) [Member]
Variable Interest Entity [Line Items]
Sponsored investment products	(11)	(11)
Maximum Risk of Loss [Member]
Variable Interest Entity [Line Items]
Sponsored investment products	$ 2,448	$ 2,510