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
	Mar. 31, 2024	Mar. 31, 2023	Jan. 01, 2024	Jan. 01, 2023
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	$ 1,232	$ 986
Amortized Cost without Allowance	1,070	1,571
Total	2,302	2,557
Amortized Cost			$ 2,166	$ 2,439
Interest Income Recognized	13	17
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	590	227
Amortized Cost without Allowance	274	342
Total	864	569
Amortized Cost			670	504
Interest Income Recognized	2	3
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	379	364
Amortized Cost without Allowance	476	966
Total	855	1,330
Amortized Cost			869	1,240
Interest Income Recognized	6	5
Residential Builder and Developer [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	3	3
Total	3	3
Amortized Cost			3	1
Other Commercial Construction [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	33	94
Amortized Cost without Allowance	108	49
Total	141	143
Amortized Cost			171	125
Interest Income Recognized		2
Residential [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	82	125
Amortized Cost without Allowance	120	129
Total	202	254
Amortized Cost			215	272
Interest Income Recognized	3	5
Residential Limited Documentation [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	18	40
Amortized Cost without Allowance	35	29
Total	53	69
Amortized Cost			55	78
Interest Income Recognized	1
Home Equity Lines and Loans [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	48	39
Amortized Cost without Allowance	39	42
Total	87	81
Amortized Cost			81	85
Interest Income Recognized	1	2
Recreational Finance [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	18	24
Amortized Cost without Allowance	12	10
Total	30	34
Amortized Cost			36	45
Automobile [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	7	23
Amortized Cost without Allowance	6	4
Total	13	27
Amortized Cost			14	40
Other [Member]
Financing Receivable, Impaired [Line Items]
Amortized Cost with Allowance	54	47
Total	$ 54	$ 47
Amortized Cost			$ 52	$ 49