Segment Information - Information about Company's Segments (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Net Interest Income	$ 1,695	$ 1,680
Noninterest income	611	580
Provision for credit losses	130	200
Salaries and employee benefits	887	833
Depreciation and amortization	83	80
Income before taxes	761	664
Income tax expense (benefit)	177	133
Net income (loss)	584	531
Operating Segments
Segment Reporting Information [Line Items]
Total revenue	2,306	2,260
Depreciation and amortization	130	130
Other direct expenses	398	433
Indirect expense	0	0
Income before taxes	761	664
Income tax expense (benefit)	177	133
Average total assets	208,321	211,478
Commercial Bank
Segment Reporting Information [Line Items]
Other direct expenses	67	66
Average total assets		81,083
Commercial Bank | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income	529	548
Noninterest income	173	151
Total revenue	702	699
Provision for credit losses	36	77
Salaries and employee benefits	151	146
Depreciation and amortization	10	9
Indirect expense	123	124
Income before taxes	315	277
Income tax expense (benefit)	84	76
Net income (loss)	231	201
Average total assets	79,362
Retail Bank
Segment Reporting Information [Line Items]
Other direct expenses	99	100
Average total assets		52,232
Retail Bank | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income	972	1,071
Noninterest income	208	197
Total revenue	1,180	1,268
Provision for credit losses	79	68
Salaries and employee benefits	196	190
Depreciation and amortization	62	65
Indirect expense	279	244
Income before taxes	465	601
Income tax expense (benefit)	118	155
Net income (loss)	347	446
Average total assets	54,381
Institutional Services and Wealth Management
Segment Reporting Information [Line Items]
Other direct expenses	26	28
Institutional Services and Wealth Management | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income	171	186
Noninterest income	209	191
Total revenue	380	377
Provision for credit losses	3	0
Salaries and employee benefits	106	100
Depreciation and amortization	2	2
Indirect expense	81	75
Income before taxes	162	172
Income tax expense (benefit)	41	44
Net income (loss)	121	128
Average total assets	4,102	3,636
All Other | Operating Segments
Segment Reporting Information [Line Items]
Net Interest Income	23	(125)
Noninterest income	21	41
Total revenue	44	(84)
Provision for credit losses	12	55
Salaries and employee benefits	434	397
Depreciation and amortization	56	54
Other direct expenses	206	239
Indirect expense	(483)	(443)
Income before taxes	(181)	(386)
Income tax expense (benefit)	(66)	(142)
Net income (loss)	(115)	(244)
Average total assets	$ 70,476	$ 74,527