Collateralized Agreements and Financings - Other Secured Financings (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	$ 10,100	$ 13,218
Other Secured Financings Long Term At Fair Value	8,108	10,908
Other Secured Financings Long Term At Amortized Cost	1,477	1,629
Total other secured financings	19,685	25,755
Other secured financings collateralized by financial instruments	14,097	16,909
Other secured financings collateralized by other assets	5,588	8,846
U.S. Dollar [Member]
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	4,768	6,371
Other Secured Financings Long Term At Fair Value	3,812	6,632
Other Secured Financings Long Term At Amortized Cost	813	914
Total other secured financings	9,393	13,917
Other secured financings collateralized by financial instruments	5,154	6,841
Other secured financings collateralized by other assets	4,239	7,076
Non-U.S. Dollar [Member]
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	5,332	6,847
Other Secured Financings Long Term At Fair Value	4,296	4,276
Other Secured Financings Long Term At Amortized Cost	664	715
Total other secured financings	10,292	11,838
Other secured financings collateralized by financial instruments	8,943	10,068
Other secured financings collateralized by other assets	$ 1,349	$ 1,770