v3.26.1
Borrowings - Carrying Value and Fair Value of Long-Term Borrowings Determined Market Prices EUR/USD Foreign Exchange Rate (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Debt Instrument [Line Items]    
Maturity Amount $ 12,843  
Unamortized Discount and Debt Issuance Costs [1] (99)  
Carrying Value 12,744 $ 12,768
Fair Value 12,343 $ 12,500
3.20% Notes due 2027 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 700  
Unamortized Discount and Debt Issuance Costs [1],[2] 0  
Carrying Value [2] 700  
Fair Value [2] 695  
4.60% Notes due 2027 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 800  
Unamortized Discount and Debt Issuance Costs [1] (1)  
Carrying Value 799  
Fair Value 803  
4.70% Notes due 2029 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 500  
Unamortized Discount and Debt Issuance Costs [1] (1)  
Carrying Value 499  
Fair Value 505  
3.25% Notes due 2029 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (4)  
Carrying Value [2] 996  
Fair Value [2] 970  
2.40% Notes due 2030 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (2)  
Carrying Value [2] 998  
Fair Value [2] 924  
1.90% Notes due 2031 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,250  
Unamortized Discount and Debt Issuance Costs [1],[2] (5)  
Carrying Value [2] 1,245  
Fair Value [2] 1,112  
2.10% Notes due 2032 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,000  
Unamortized Discount and Debt Issuance Costs [1],[2] (9)  
Carrying Value [2] 991  
Fair Value [2] 873  
4.75% Notes due 2033 [Member]    
Debt Instrument [Line Items]    
Maturity Amount [2] 1,250  
Unamortized Discount and Debt Issuance Costs [1],[2] (15)  
Carrying Value [2] 1,235  
Fair Value [2] 1,251  
5.00% Notes due 2034 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,000  
Unamortized Discount and Debt Issuance Costs [1] (6)  
Carrying Value 994  
Fair Value 1,005  
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 499  
3.75% Notes due 2035 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,143  
Unamortized Discount and Debt Issuance Costs [1] (7)  
Carrying Value 1,136  
Fair Value 1,156  
5.25% Notes due 2054 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,500  
Unamortized Discount and Debt Issuance Costs [1] (30)  
Carrying Value 1,470  
Fair Value 1,408  
5.35% Notes due 2055 [Member]    
Debt Instrument [Line Items]    
Maturity Amount 1,200  
Unamortized Discount and Debt Issuance Costs (14)  
Carrying Value 1,186  
Fair Value $ 1,142  
[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.