Business Segment Information - Nonoperating Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Personnel expense	$ 282	$ 279	$ 561	$ 580
Net occupancy expense	34	31	69	62
Computer software	34	29	66	59
Operations services	23	23	46	45
Legal and professional fees	17	18	31	33
Deposit insurance expense	12	16	25	40
Advertising and public relations	14	14	24	22
Equipment expense	11	11	22	22
Amortization of intangible assets	10	11	20	22
Contract employment and outsourcing	8	14	16	28
Communications and delivery	8	8	16	16
Other expense	38	46	82	86
Cost allocations	0	0	0	0
Total noninterest expense	491	500	978	1,015
Commercial, Consumer & Wealth
Disaggregation of Revenue [Line Items]
Personnel expense	133	133	268	272
Net occupancy expense	20	19	41	37
Computer software	8	8	15	16
Operations services	4	4	8	9
Legal and professional fees	3	2	6	5
Deposit insurance expense	0	0	0	0
Advertising and public relations	2	2	3	4
Equipment expense	3	3	5	6
Amortization of intangible assets	9	10	17	19
Contract employment and outsourcing	1	1	2	2
Communications and delivery	2	3	5	5
Other expense	15	22	32	43
Cost allocations	154	150	296	286
Total noninterest expense	354	357	698	704
Wholesale
Disaggregation of Revenue [Line Items]
Personnel expense	52	48	103	98
Net occupancy expense	2	2	4	4
Computer software	2	1	3	3
Operations services	6	6	11	11
Legal and professional fees	1	1	2	1
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	2	2
Communications and delivery	1	1	2	2
Other expense	5	6	9	10
Cost allocations	6	7	13	15
Total noninterest expense	76	73	151	148
Corporate
Disaggregation of Revenue [Line Items]
Personnel expense	97	98	190	210
Net occupancy expense	12	10	24	21
Computer software	24	20	48	40
Operations services	13	13	27	25
Legal and professional fees	13	15	23	27
Deposit insurance expense	12	16	25	40
Advertising and public relations	12	12	21	18
Equipment expense	8	8	16	15
Amortization of intangible assets	1	1	2	2
Contract employment and outsourcing	6	12	12	24
Communications and delivery	5	4	9	9
Other expense	18	18	41	33
Cost allocations	(160)	(157)	(309)	(301)
Total noninterest expense	$ 61	$ 70	$ 129	$ 163