Business Segment Information - Nonoperating Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Personnel expense	$ 296	$ 282	$ 856	$ 862
Net occupancy expense	36	33	105	95
Computer software	34	30	100	89
Operations services	24	25	71	69
Legal and professional fees	24	15	54	47
Deposit insurance expense	11	11	36	51
Advertising and public relations	12	14	36	37
Equipment expense	10	10	32	32
Amortization of intangible assets	9	11	29	33
Contract employment and outsourcing	11	12	27	40
Communications and delivery	8	8	25	24
Contributions	23	4	25	6
Other expense	52	56	133	142
Cost allocations	0	0	0	0
Total noninterest expense	550	511	1,529	1,527
Commercial, Consumer & Wealth
Disaggregation of Revenue [Line Items]
Personnel expense	136	133	403	405
Net occupancy expense	20	19	59	56
Computer software	8	8	23	24
Operations services	5	4	13	13
Legal and professional fees	5	3	12	8
Deposit insurance expense	0	0	0	0
Advertising and public relations	2	2	5	6
Equipment expense	2	3	8	9
Amortization of intangible assets	9	10	26	29
Contract employment and outsourcing	1	1	3	3
Communications and delivery	2	3	7	8
Contributions	0	0	1	1
Other expense	14	16	46	58
Cost allocations	161	150	457	436
Total noninterest expense	365	352	1,063	1,056
Wholesale
Disaggregation of Revenue [Line Items]
Personnel expense	56	50	159	148
Net occupancy expense	2	2	7	7
Computer software	2	1	5	4
Operations services	6	5	17	16
Legal and professional fees	1	1	2	2
Deposit insurance expense	0	0	0	0
Advertising and public relations	0	0	0	0
Equipment expense	0	0	1	1
Amortization of intangible assets	0	0	1	1
Contract employment and outsourcing	1	1	3	3
Communications and delivery	1	1	3	2
Contributions	0	0	0	0
Other expense	6	6	17	17
Cost allocations	8	8	20	22
Total noninterest expense	83	75	235	223
Corporate
Disaggregation of Revenue [Line Items]
Personnel expense	104	99	294	309
Net occupancy expense	14	12	39	32
Computer software	24	21	72	61
Operations services	13	16	41	40
Legal and professional fees	18	11	40	37
Deposit insurance expense	11	11	36	51
Advertising and public relations	10	12	31	31
Equipment expense	8	7	23	22
Amortization of intangible assets	0	1	2	3
Contract employment and outsourcing	9	10	21	34
Communications and delivery	5	4	15	14
Contributions	23	4	24	5
Other expense	32	34	70	67
Cost allocations	(169)	(158)	(477)	(458)
Total noninterest expense	$ 102	$ 84	$ 231	$ 248