Loans and Leases and the Allowance for Credit Losses - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	$ 1,410	$ 1,724
Accruing Loans Past Due 90 Days or More	297	339
Nonaccrual	2,302	2,166
Loans and leases, net of unearned discount	134,973	134,068
Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	130,964	129,839
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	219	238
Accruing Loans Past Due 90 Days or More	11	11
Nonaccrual	864	670
Loans and leases, net of unearned discount	57,897	57,010
Commercial and Industrial [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	56,803	56,091
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	163	311
Accruing Loans Past Due 90 Days or More	31	25
Nonaccrual	855	869
Loans and leases, net of unearned discount	25,168	25,277
Commercial [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	24,119	24,072
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	48	5
Nonaccrual	3	3
Loans and leases, net of unearned discount	1,035	1,073
Residential Builder and Developer [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	984	1,065
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	155	159
Accruing Loans Past Due 90 Days or More	2	1
Nonaccrual	141	171
Loans and leases, net of unearned discount	6,213	6,653
Other Commercial Construction [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,915	6,322
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	627	763
Accruing Loans Past Due 90 Days or More	245	295
Nonaccrual	202	215
Loans and leases, net of unearned discount	22,192	22,353
Residential [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	21,118	21,080
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	30	31
Nonaccrual	53	55
Loans and leases, net of unearned discount	884	911
Residential Limited Documentation [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	801	825
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	34	40
Nonaccrual	87	81
Loans and leases, net of unearned discount	4,558	4,649
Home Equity Lines and Loans [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,437	4,528
Recreational Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	71	87
Nonaccrual	30	36
Loans and leases, net of unearned discount	10,654	10,058
Recreational Finance [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,553	9,935
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	43	60
Nonaccrual	13	14
Loans and leases, net of unearned discount	4,308	3,992
Automobile [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,252	3,918
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-89 Days Past Due	20	30
Accruing Loans Past Due 90 Days or More	8	7
Nonaccrual	54	52
Loans and leases, net of unearned discount	2,064	2,092
Other [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,982	$ 2,003