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		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Jan. 01, 2024	Mar. 31, 2023	Jan. 01, 2023
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 1,056	$ 883	$ 1,056	$ 883
Amortized Cost without Allowance	968	1,553	968	1,553
Total	2,024	2,436	2,024	2,436
Amortized Cost					$ 2,302	$ 2,166	$ 2,557	$ 2,439
Interest Income Recognized	34	13	47	30
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	494	202	494	202
Amortized Cost without Allowance	311	405	311	405
Total	805	607	805	607
Amortized Cost					864	670	569	504
Interest Income Recognized	7	3	9	6
Commercial Real Estate | Commercial
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	315	376	315	376
Amortized Cost without Allowance	392	816	392	816
Total	707	1,192	707	1,192
Amortized Cost					855	869	1,330	1,240
Interest Income Recognized	20	4	26	9
Commercial Real Estate | Residential builder and developer
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	2	1	2	1
Amortized Cost without Allowance	0	0	0	0
Total	2	1	2	1
Amortized Cost					3	3	3	1
Interest Income Recognized	0	0	0	0
Commercial Real Estate | Other commercial construction
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	13	44	13	44
Amortized Cost without Allowance	64	102	64	102
Total	77	146	77	146
Amortized Cost					141	171	143	125
Interest Income Recognized	3	0	3	2
Residential Real Estate | Residential
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	95	91	95	91
Amortized Cost without Allowance	110	148	110	148
Total	205	239	205	239
Amortized Cost					202	215	254	272
Interest Income Recognized	3	4	6	9
Residential Real Estate | Residential — limited documentation
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	20	28	20	28
Amortized Cost without Allowance	35	39	35	39
Total	55	67	55	67
Amortized Cost					53	55	69	78
Interest Income Recognized	0	0	1	0
Consumer: | Home equity lines and loans
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	37	49	37	49
Amortized Cost without Allowance	42	28	42	28
Total	79	77	79	77
Amortized Cost					87	81	81	85
Interest Income Recognized	1	2	2	4
Consumer: | Recreational finance
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	15	23	15	23
Amortized Cost without Allowance	10	9	10	9
Total	25	32	25	32
Amortized Cost					30	36	34	45
Interest Income Recognized	0	0	0	0
Consumer: | Automobile
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	7	18	7	18
Amortized Cost without Allowance	4	4	4	4
Total	11	22	11	22
Amortized Cost					13	14	27	40
Interest Income Recognized	0	0	0	0
Consumer: | Other
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	58	51	58	51
Amortized Cost without Allowance	0	2	0	2
Total	58	53	58	53
Amortized Cost					$ 54	$ 52	$ 47	$ 49
Interest Income Recognized	$ 0	$ 0	$ 0	$ 0