v3.25.2
Borrowings - Carrying Value and Fair Value of Long-Term Borrowings Determined Market Prices EUR/USD Foreign Exchange Rate (Detail) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Debt Instrument [Line Items]    
Maturity Amount $ 12,874  
Unamortized Discount and Debt Issuance Costs [1] (112)  
Carrying Value 12,762 $ 12,314
Fair Value 12,449 $ 11,700
3.20% Notes due 2027 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 700  
Unamortized Discount and Debt Issuance Costs [1],[2] (1)  
Carrying Value [2] 699  
Fair Value [2] 691  
4.60% Notes due 2027 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 800  
Unamortized Discount and Debt Issuance Costs [1] (2)  
Carrying Value 798  
Fair Value 810  
3.25% Notes due 2029 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (5)  
Carrying Value [2] 995  
Fair Value [2] 969  
4.70% Notes due 2029 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 500  
Unamortized Discount and Debt Issuance Costs [1] (3)  
Carrying Value 497  
Fair Value 510  
2.40% Notes due 2030 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (3)  
Carrying Value [2] 997  
Fair Value [2] 920  
1.90% Notes due 2031 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,250  
Unamortized Discount and Debt Issuance Costs [1],[2] (6)  
Carrying Value [2] 1,244  
Fair Value [2] 1,098  
2.10% Notes due 2032 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (10)  
Carrying Value [2] 990  
Fair Value [2] 861  
4.75% Notes due 2033 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,250  
Unamortized Discount and Debt Issuance Costs [1],[2] (16)  
Carrying Value [2] 1,234  
Fair Value [2] 1,261  
5.00% Notes due 2034 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,000  
Unamortized Discount and Debt Issuance Costs [1] (7)  
Carrying Value 993  
Fair Value 1,021  
4.90% Notes due 2035 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 500  
Unamortized Discount and Debt Issuance Costs [1] (5)  
Carrying Value 495  
Fair Value 504  
3.75% Notes due 2035 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,174  
Unamortized Discount and Debt Issuance Costs [1] (8)  
Carrying Value 1,166  
Fair Value 1,196  
5.25% Notes due 2054 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,500  
Unamortized Discount and Debt Issuance Costs [1] (32)  
Carrying Value 1,468  
Fair Value 1,441  
5.35% Notes due 2055 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,200  
Unamortized Discount and Debt Issuance Costs [1] (14)  
Carrying Value 1,186  
Fair Value $ 1,167  
[1] The unamortized discount and debt issuance costs are amortized over the term of the notes.
[2] Issued by Old BlackRock and guaranteed by BlackRock, Inc.