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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		6 Months Ended
	May 30, 2023	Jul. 31, 2025	Jan. 31, 2025	Jun. 30, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted				136,902
Fair value of RSUs/restricted stock granted to employees				$ 690
Awards vesting				54,212
Reduction of shares due to performance measures				(71,866)
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of outstanding RSUs				$ 2,400
Stock price				$ 1,049
Unrecognized stock-based compensation expense				$ 1,200
Remaining weighted-average period				2 years 1 month 6 days
Restricted Stock Units (RSUs) [Member] \| HPS Transaction [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted		680,000
Award vesting period, years		5 years
Restricted Stock Units And Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted			332,000
Award vesting period, years			3 years
Awards to employees cliff vesting			216,000
RSUs to employees that cliff vest, percentage			100.00%
RSUs to employees that cliff vest, date			Jan. 31, 2028
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted				136,133
Award vesting period, years			3 years
Awards to employees cliff vesting			136,000
RSUs to employees that cliff vest, percentage			100.00%
RSUs to employees that cliff vest, date			Jan. 31, 2028
Share based compensation vesting option exercised period				up to nine years
Intrinsic value of outstanding RSUs				$ 681
Stock price				$ 1,049
Unrecognized stock-based compensation expense				$ 342
Remaining weighted-average period				2 years 2 months 12 days
Awards vesting				54,212
Reduction of shares due to performance measures			(71,866)	(71,866)
Fair value of RSUs/restricted stock granted to employees				$ 77
Performance Based Restricted Stock Units [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
Performance Based Restricted Stock Units [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
Performance Based Restricted Stock Units [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
Performance Based Restricted Stock Units [Member] \| GIP Transaction [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted				769
Awards vesting				0
Reduction of shares due to performance measures				0
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	4 years			5 years
Award vesting period of BlackRock's performance period	3 years
Award performance measurement period				4 years
Aggregate intrinsic value of options exercised				$ 89
Unrecognized stock-based compensation expense				$ 88
Performance Based Stock Options [Member] \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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]
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]
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				3 years 2 months 12 days
Unrecognized stock-based compensation expense				$ 88
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
Cliff vesting RSU [Member] \| HPS Transaction [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Units, Granted		270,000
Award vesting period, years		6 months
RSUs to employees that cliff vest, percentage		100.00%