Lines of business - Contribution of Segments to Overall Profitability (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
Segment Reporting Information [Line Items]
Total fee and other revenue	$ 3,394	$ 3,315	$ 3,144	$ 9,975	$ 9,668
Net interest revenue (expense)	641	645	703	1,941	2,297
Provision for credit losses	(45)	(86)	9	(214)	321
Noninterest expense	2,918	2,778	2,681	8,547	8,079
Net income (loss) attributable to noncontrolling interests	(4)	5	7	6	4
Operating segments
Segment Reporting Information [Line Items]
Total fee and other revenue	3,398	3,310	3,137	9,969	9,664
Net interest revenue (expense)	641	645	703	1,941	2,297
Total revenue (loss)	4,039	3,955	3,840	11,910	11,961
Provision for credit losses	(45)	(86)	9	(214)	321
Noninterest expense	2,918	2,778	2,681	8,547	8,079
Income (loss) before taxes	$ 1,166	$ 1,263	$ 1,150	$ 3,577	$ 3,561
Pre-tax operating margin	29.00%	32.00%	30.00%	30.00%	30.00%
Average assets	$ 446,761	$ 452,329	$ 414,865	$ 453,106	$ 405,203
Operating segments | Investment Services
Segment Reporting Information [Line Items]
Total fee and other revenue	2,378	2,336	2,246	7,059	7,021
Net interest revenue (expense)	632	643	681	1,920	2,255
Total revenue (loss)	3,010	2,979	2,927	8,979	9,276
Provision for credit losses	(35)	(77)	(10)	(191)	284
Noninterest expense	2,211	2,052	2,020	6,364	5,996
Income (loss) before taxes	$ 834	$ 1,004	$ 917	$ 2,806	$ 2,996
Pre-tax operating margin	28.00%	34.00%	31.00%	31.00%	32.00%
Average assets	$ 379,273	$ 383,330	$ 329,324	$ 382,531	$ 322,924
Operating segments | Investment and Wealth Management
Segment Reporting Information [Line Items]
Total fee and other revenue	985	952	871	2,880	2,555
Net interest revenue (expense)	47	47	47	142	147
Total revenue (loss)	1,032	999	918	3,022	2,702
Provision for credit losses	(7)	(4)	12	(7)	28
Noninterest expense	691	677	661	2,077	2,014
Income (loss) before taxes	$ 348	$ 326	$ 245	$ 952	$ 660
Pre-tax operating margin	34.00%	33.00%	27.00%	31.00%	24.00%
Average assets	$ 30,195	$ 30,370	$ 30,160	$ 30,870	$ 30,343
Net income (loss) attributable to noncontrolling interests	(4)	5	7	6	4
Operating segments | Other
Segment Reporting Information [Line Items]
Total fee and other revenue	35	22	20	30	88
Net interest revenue (expense)	(38)	(45)	(25)	(121)	(105)
Total revenue (loss)	(3)	(23)	(5)	(91)	(17)
Provision for credit losses	(3)	(5)	7	(16)	9
Noninterest expense	16	49	0	106	69
Income (loss) before taxes	(16)	(67)	(12)	(181)	(95)
Average assets	$ 37,293	$ 38,629	$ 55,381	$ 39,705	$ 51,936