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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		3 Months Ended	9 Months Ended
	May 30, 2023	Oct. 31, 2024	Jan. 31, 2024	Mar. 31, 2024	Sep. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted					864,219
Fair value of RSUs/restricted stock granted to employees					$ 693
Awards vesting					760,294
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period, years					5 years
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period, years					2 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted			347,000
Award vesting period, years			3 years
Awards to employees cliff vesting			344,000
RSUs to employees that cliff vest, percentage			100.00%
RSUs to employees that cliff vest, date			Jan. 31, 2027
Intrinsic value of outstanding RSUs					$ 1,700
Stock price					$ 949.51
Unrecognized stock-based compensation expense					$ 645
Remaining weighted-average period					1 year 4 months 24 days
Restricted Stock Units (RSUs) [Member] \| GIP Transaction [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted				106,000
Restricted Stock Units (RSUs) [Member] \| GIP Transaction [Member] \| Subsequent Event Member
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards to employees cliff vesting		500,000
RSUs to employees that cliff vest, percentage		100.00%
RSUs to employees that cliff vest, date		Oct. 01, 2029
Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted					165,631
Award vesting period, years			3 years
Awards to employees cliff vesting			165,631
RSUs to employees that cliff vest, percentage			100.00%
RSUs to employees that cliff vest, date			Jan. 31, 2027
Share based compensation vesting option exercised period					up to nine years
Intrinsic value of outstanding RSUs					$ 429
Stock price					$ 949.51
Unrecognized stock-based compensation expense					$ 151
Remaining weighted-average period					1 year 6 months
Awards vesting					115,631
Reduction of shares due to performance measures			(42,341)		(42,341)
Fair value of RSUs/restricted stock granted to employees					$ 101
Performance-Based RSUs [Member] \| GIP Transaction [Member] \| Subsequent Event Member
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting		200,000
Performance Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares awarded to purchase	814,482
Share based compensation vesting option exercised period					up to nine years
Award vesting percentage of BlackRock's grant-date stock price	130.00%				125.00%
Award vesting period of BlackRock's grant-date stock price					5 years
Award performance measurement period					4 years
Aggregate intrinsic value of options exercised					$ 150
Performance Based Stock Options [Member] \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	25.00%
RSUs to employees that cliff vest, vesting date	May 30, 2027
Service year of awards					2022
Performance Based Stock Options [Member] \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	25.00%
RSUs to employees that cliff vest, vesting date	May 30, 2028
Service year of awards					2023
Performance Based Stock Options [Member] \| Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	50.00%
RSUs to employees that cliff vest, vesting date	May 30, 2029
Service year of awards					2024
Time-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares awarded to purchase	326,391
Share based compensation vesting option exercised period	up to nine years
Remaining weighted-average period					2 years 8 months 12 days
Unrecognized stock-based compensation expense					$ 122
Time-based stock options \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	25.00%
RSUs to employees that cliff vest, vesting date	May 30, 2027
Time-based stock options \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	25.00%
RSUs to employees that cliff vest, vesting date	May 30, 2028
Time-based stock options \| Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs to employees that cliff vest, percentage	50.00%
RSUs to employees that cliff vest, vesting date	May 30, 2029