Business Segment Information - Noninterest Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Personnel expense	$ 289	$ 279
Computer software	38	32
Net occupancy expense	35	35
Operations services	25	23
Legal and professional fees	16	14
Deposit insurance expense	13	13
Equipment expense	11	10
Advertising and public relations	10	10
Amortization of intangible assets	8	10
Other expense	60	61
Cost allocations	0	0
Total noninterest expense	505	487
Commercial, Consumer & Wealth
Disaggregation of Revenue [Line Items]
Personnel expense	142	135
Computer software	8	7
Net occupancy expense	18	21
Operations services	4	4
Legal and professional fees	4	3
Deposit insurance expense	0	0
Equipment expense	3	2
Advertising and public relations	1	1
Amortization of intangible assets	8	9
Other expense	17	19
Cost allocations	163	143
Total noninterest expense	368	344
Wholesale
Disaggregation of Revenue [Line Items]
Personnel expense	56	51
Computer software	2	2
Net occupancy expense	3	2
Operations services	6	6
Legal and professional fees	1	1
Deposit insurance expense	0	0
Equipment expense	0	0
Advertising and public relations	0	0
Amortization of intangible assets	0	0
Other expense	7	7
Cost allocations	8	6
Total noninterest expense	83	75
Corporate
Disaggregation of Revenue [Line Items]
Personnel expense	91	93
Computer software	28	23
Net occupancy expense	14	12
Operations services	15	13
Legal and professional fees	11	10
Deposit insurance expense	13	13
Equipment expense	8	8
Advertising and public relations	9	9
Amortization of intangible assets	0	1
Other expense	36	35
Cost allocations	(171)	(149)
Total noninterest expense	$ 54	$ 68