Business Segment Information - Nonoperating Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Personnel expense	$ 279	$ 301
Net occupancy expense	35	31
Computer software	32	30
Operations services	23	21
Legal and professional fees	14	14
Deposit insurance expense	13	24
Advertising and public relations	10	8
Amortization of intangible assets	10	11
Equipment expense	10	11
Contract employment and outsourcing	8	13
Communications and delivery	8	8
Other expense	45	43
Cost allocations	0	0
Total noninterest expense	487	515
Commercial, Consumer & Wealth
Disaggregation of Revenue [Line Items]
Personnel expense	135	139
Net occupancy expense	21	19
Computer software	7	8
Operations services	4	4
Legal and professional fees	3	2
Deposit insurance expense	0	0
Advertising and public relations	1	2
Amortization of intangible assets	9	10
Equipment expense	2	3
Contract employment and outsourcing	1	1
Communications and delivery	2	2
Other expense	17	21
Cost allocations	141	136
Total noninterest expense	343	347
Wholesale
Disaggregation of Revenue [Line Items]
Personnel expense	51	51
Net occupancy expense	2	2
Computer software	2	1
Operations services	6	6
Legal and professional fees	1	0
Deposit insurance expense	0	0
Advertising and public relations	0	0
Amortization of intangible assets	0	0
Equipment expense	0	0
Contract employment and outsourcing	1	1
Communications and delivery	1	1
Other expense	5	5
Cost allocations	8	8
Total noninterest expense	77	75
Corporate
Disaggregation of Revenue [Line Items]
Personnel expense	93	111
Net occupancy expense	12	10
Computer software	23	21
Operations services	13	11
Legal and professional fees	10	12
Deposit insurance expense	13	24
Advertising and public relations	9	6
Amortization of intangible assets	1	1
Equipment expense	8	8
Contract employment and outsourcing	6	11
Communications and delivery	5	5
Other expense	23	17
Cost allocations	(149)	(144)
Total noninterest expense	$ 67	$ 93