v3.20.4
Related Party Transactions - Additional Information (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Related Party Transaction [Line Items]    
Due from related parties $ 109 $ 119
Due to related parties 17 12
BlackRock Mutual Funds and iShares ETFs [Member]    
Related Party Transaction [Line Items]    
Accounts receivable from related parties $ 1,100 $ 995