Borrowings - Additional Information (Detail) £ in Millions		3 Months Ended	9 Months Ended
		Mar. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 GBP (£)	May 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Aggregate principal amount			$ 12,481,000,000
Line of credit facility, covenant terms			The 2024 Credit Facility permits the Company to request up to an additional $1.0 billion of borrowing capacity, subject to lender credit approval, which could increase the overall size of the 2024 Credit Facility to an aggregate principal amount of up to $6.4 billion. Interest on outstanding borrowings accrues at an applicable benchmark rate for the denominated currency of the loan, plus a spread. The 2024 Credit Facility requires the Company not to exceed a maximum leverage ratio (ratio of net debt to earnings before interest, taxes, depreciation and amortization, where net debt equals total debt less unrestricted cash) of 3 to 1
Borrowings			$ 12,370,000,000				$ 7,918,000,000
Fair Value			12,279,000,000				$ 7,400,000,000
Repayments of long-term borrowings			1,000,000,000	$ 0
Commercial Paper [Member]
Debt Instrument [Line Items]
Maximum amount available under facility			4,000,000,000
Amount outstanding under credit facility			0
2024 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Unsecured revolving credit facility			5,400,000,000			$ 400,000,000
Additional amount available, subject to lender credit approval			1,000,000,000
Maximum amount available under facility			$ 6,400,000,000
Line of credit facility, interest rate description			Interest on outstanding borrowings accrues at an applicable benchmark rate for the denominated currency of the loan, plus a spread.
Amount outstanding under credit facility			$ 0
Line of credit facility, covenant compliance			less than 1 to 1
2024 Subsidiary Credit Facility [Member] | Subsidiaries [Member]
Debt Instrument [Line Items]
Maximum amount available under facility			$ 34,000,000		£ 25
Amount outstanding under credit facility			0
March 2024 Notes
Debt Instrument [Line Items]
Aggregate principal amount			3,000,000,000
Debt instrument, Approximate annual interest expense			$ 152,000,000
Debt instrument, payment terms			Interest on the March 2024 Notes of approximately $152 million per year is payable semi-annually on March 14 and September 14 of each year, which commenced on September 14, 2024.
July 2024 Notes
Debt Instrument [Line Items]
Aggregate principal amount			$ 2,500,000,000
July 2027 Notes
Debt Instrument [Line Items]
Debt instrument, Approximate annual interest expense			$ 37,000,000
Debt instrument, payment terms			Interest on the 2027 Notes of approximately $37 million per year is payable semi-annually on January 26 and July 26 of each year, beginning January 26, 2025.
July 2035 Notes
Debt Instrument [Line Items]
Debt instrument, Approximate annual interest expense			$ 25,000,000
Debt instrument, payment terms			Interest on the 2035 Notes and 2055 Notes of approximately $25 million and $64 million per year, respectively, is payable semi-annually on January 8 and July 8 of each year, beginning January 8, 2025.
July 2055 Notes
Debt Instrument [Line Items]
Debt instrument, Approximate annual interest expense			$ 64,000,000
Debt instrument, payment terms			Interest on the 2035 Notes and 2055 Notes of approximately $25 million and $64 million per year, respectively, is payable semi-annually on January 8 and July 8 of each year, beginning January 8, 2025.
Unsecured Debt Two Thousand Twenty Seven Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, redemption price, percentage of principal amount redeemed			101.00%
4.70% Notes due 2029 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 500,000,000
Debt instrument, interest rate			4.70%		4.70%
Debt instrument, maturity date			Mar. 14, 2029
Borrowings	[1]		$ 497,000,000
Fair Value	[1]		514,000,000
5.00% Notes due 2034 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 1,000,000,000
Debt instrument, interest rate			5.00%		5.00%
Debt instrument, maturity date			Mar. 14, 2034
Borrowings	[1]		$ 993,000,000
Fair Value	[1]		1,040,000,000
5.25% Notes due 2054 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 1,500,000,000
Debt instrument, interest rate			5.25%		5.25%
Debt instrument, maturity date			Mar. 14, 2054
Borrowings	[1]		$ 1,468,000,000
Fair Value	[1]		1,549,000,000
4.60% Notes due 2027 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 800,000,000
Debt instrument, interest rate			4.60%		4.60%
Debt instrument, maturity date			Jul. 26, 2027
Borrowings	[1]		$ 798,000,000
Fair Value	[1]		815,000,000
4.90% Notes due 2035 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 500,000,000
Debt instrument, interest rate			4.90%		4.90%
Debt instrument, maturity date			Jan. 08, 2035
Borrowings	[1]		$ 495,000,000
Fair Value	[1]		515,000,000
5.35% Notes due 2055 [Member]
Debt Instrument [Line Items]
Aggregate principal amount	[1]		$ 1,200,000,000
Debt instrument, interest rate			5.35%		5.35%
Debt instrument, maturity date			Jan. 08, 2055
Borrowings	[1]		$ 1,187,000,000
Fair Value	[1]		$ 1,260,000,000
3.50% Notes due 2024 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		3.50%
Repayments of long-term borrowings		$ 1,000,000,000

[1] Issued by BlackRock Funding and guaranteed by BlackRock.