Interest Income and Interest Expense - Interest Income and Interest Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income and expense
Deposits with banks	$ 11	$ 287	$ 234	$ 981
Collateralized agreements	(67)	1,100	451	3,705
Trading assets	1,176	1,472	4,006	4,390
Investments	404	340	1,196	1,052
Loans	1,153	1,379	3,691	4,075
Other interest	255	881	1,138	2,613
Total interest income	2,932	5,459	10,716	16,816
Deposits	505	945	1,982	2,689
Collateralized financings	50	710	570	2,130
Trading liabilities	345	254	931	935
Short-term borrowings	124	190	423	500
Long-term borrowings	981	1,321	3,217	4,119
Other interest	(157)	1,031	252	3,146
Total interest expense	1,848	4,451	7,375	13,519
Net interest income	$ 1,084	$ 1,008	$ 3,341	$ 3,297