Net interest revenue (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest revenue
Deposits with the Federal Reserve and other central banks	$ (21)	$ (25)	$ (10)	$ (62)	$ 63
Deposits with banks	12	11	20	37	118
Federal funds sold and securities purchased under resale agreements	32	25	48	89	505
Margin loans	52	49	41	146	168
Non-margin loans	186	188	199	559	738
Securities:
Taxable	413	415	499	1,278	1,649
Exempt from federal income taxes	11	11	7	31	19
Total securities	424	426	506	1,309	1,668
Trading securities	8	11	16	38	73
Total interest revenue	693	685	820	2,116	3,333
Interest expense
Deposits	(44)	(49)	(29)	(130)	194
Federal funds purchased and securities sold under repurchase agreements	2	(5)	6	(6)	282
Trading liabilities	1	2	2	6	11
Other borrowed funds	3	1	3	6	14
Commercial paper	0	0	0	0	7
Customer payables	(1)	0	0	(2)	29
Long-term debt	91	91	135	301	499
Total interest expense	52	40	117	175	1,036
Net interest revenue	641	645	703	1,941	2,297
Provision for credit losses	(45)	(86)	9	(214)	321
Net interest revenue after provision for credit losses	$ 686	$ 731	$ 694	$ 2,155	$ 1,976