Loans and Leases and the Allowance for Credit Losses - Loan and Leases Considered Nonaccrual and Interest Income Recognized on Loans (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Jan. 01, 2024	Jun. 30, 2023	Jan. 01, 2023
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 1,235	$ 1,038	$ 1,235	$ 1,038
Amortized Cost without Allowance	691	1,304	691	1,304
Total	1,926	2,342	1,926	2,342
Amortized Cost					$ 2,024	$ 2,166	$ 2,436	$ 2,439
Interest Income Recognized	17	22	64	52
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	610	366	610	366
Amortized Cost without Allowance	200	300	200	300
Total	810	666	810	666
Amortized Cost					805	670	607	504
Interest Income Recognized	5	7	14	13
Commercial Real Estate | Commercial
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	348	417	348	417
Amortized Cost without Allowance	230	638	230	638
Total	578	1,055	578	1,055
Amortized Cost					707	869	1,192	1,240
Interest Income Recognized	5	9	31	18
Commercial Real Estate | Residential builder and developer
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	2	3	2	3
Amortized Cost without Allowance	0	0	0	0
Total	2	3	2	3
Amortized Cost					2	3	1	1
Interest Income Recognized	1	0	1	0
Commercial Real Estate | Other commercial construction
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	21	4	21	4
Amortized Cost without Allowance	63	132	63	132
Total	84	136	84	136
Amortized Cost					77	171	146	125
Interest Income Recognized	0	0	3	2
Residential Real Estate | Residential
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	113	91	113	91
Amortized Cost without Allowance	106	150	106	150
Total	219	241	219	241
Amortized Cost					205	215	239	272
Interest Income Recognized	4	3	10	12
Residential Real Estate | Residential — limited documentation
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	22	22	22	22
Amortized Cost without Allowance	35	40	35	40
Total	57	62	57	62
Amortized Cost					55	55	67	78
Interest Income Recognized	0	1	1	1
Consumer: | Home equity lines and loans
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	39	48	39	48
Amortized Cost without Allowance	43	30	43	30
Total	82	78	82	78
Amortized Cost					79	81	77	85
Interest Income Recognized	2	2	4	6
Consumer: | Recreational finance
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	17	21	17	21
Amortized Cost without Allowance	11	10	11	10
Total	28	31	28	31
Amortized Cost					25	36	32	45
Interest Income Recognized	0	0	0	0
Consumer: | Automobile
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	8	12	8	12
Amortized Cost without Allowance	3	4	3	4
Total	11	16	11	16
Amortized Cost					11	14	22	40
Interest Income Recognized	0	0	0	0
Consumer: | Other
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	55	54	55	54
Amortized Cost without Allowance	0	0	0	0
Total	55	54	55	54
Amortized Cost					$ 58	$ 52	$ 53	$ 49
Interest Income Recognized	$ 0	$ 0	$ 0	$ 0