Collateralized Agreements and Financings - Other Secured Financings (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	$ 11,728	$ 7,195
Other Secured Financings Short Term At Amortized Cost		129
Other Secured Financings Long Term At Fair Value	11,837	10,876
Other Secured Financings Long Term At Amortized Cost	1,416	1,077
Total other secured financings	24,981	19,277
Other secured financings collateralized by financial instruments	15,390	12,015
Other secured financings collateralized by other assets	9,591	7,262
U.S. Dollar [Member]
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	5,109	2,754
Other Secured Financings Short Term At Amortized Cost		129
Other Secured Financings Long Term At Fair Value	6,693	7,402
Other Secured Financings Long Term At Amortized Cost	716	397
Total other secured financings	12,518	10,682
Other secured financings collateralized by financial instruments	5,285	4,826
Other secured financings collateralized by other assets	7,233	5,856
Non-U.S. Dollar [Member]
Other Secured Financings [Line Items]
Other Secured Financings Short Term At Fair Value	6,619	4,441
Other Secured Financings Long Term At Fair Value	5,144	3,474
Other Secured Financings Long Term At Amortized Cost	700	680
Total other secured financings	12,463	8,595
Other secured financings collateralized by financial instruments	10,105	7,189
Other secured financings collateralized by other assets	$ 2,358	$ 1,406