Loans and Leases and the Allowance for Credit Losses - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 88,104,572	$ 89,043,040
30-89 Days Past Due	792,838	845,930
Accruing Loans Past Due 90 Days or More	776,751	963,399
Nonaccrual	2,134,231	2,060,083
Loans and leases, net of unearned discount	91,808,392	92,912,452
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	23,140,917	23,101,810
30-89 Days Past Due	70,716	142,208
Accruing Loans Past Due 90 Days or More	9,238	8,284
Nonaccrual	275,146	221,022
Loans and leases, net of unearned discount	23,496,017	23,473,324
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	24,237,034	24,712,643
30-89 Days Past Due	250,362	319,099
Accruing Loans Past Due 90 Days or More	76,413	31,733
Nonaccrual	1,157,686	1,069,280
Loans and leases, net of unearned discount	25,721,495	26,132,755
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,381,331	1,400,437
30-89 Days Past Due	840	2,904
Nonaccrual	2,916	3,005
Loans and leases, net of unearned discount	1,385,087	1,406,346
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	7,283,522	7,722,049
30-89 Days Past Due	112,599	17,175
Nonaccrual	50,855	111,405
Loans and leases, net of unearned discount	7,446,976	7,850,629
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	13,126,694	13,294,872
30-89 Days Past Due	249,731	239,561
Accruing Loans Past Due 90 Days or More	687,397	920,080
Nonaccrual	341,671	355,858
Loans and leases, net of unearned discount	14,405,493	14,810,371
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,050,328	1,124,520
30-89 Days Past Due	16,546	16,666
Nonaccrual	123,512	122,888
Loans and leases, net of unearned discount	1,190,386	1,264,074
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,407,958	3,476,617
30-89 Days Past Due	16,939	15,486
Nonaccrual	71,489	70,488
Loans and leases, net of unearned discount	3,496,386	3,562,591
Recreational Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	8,156,368	7,985,173
30-89 Days Past Due	33,093	40,544
Nonaccrual	31,546	27,811
Loans and leases, net of unearned discount	8,221,007	8,053,528
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,688,513	4,604,772
30-89 Days Past Due	31,707	40,064
Nonaccrual	35,350	34,037
Loans and leases, net of unearned discount	4,755,570	4,678,873
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,631,907	1,620,147
30-89 Days Past Due	10,305	12,223
Accruing Loans Past Due 90 Days or More	3,703	3,302
Nonaccrual	44,060	44,289
Loans and leases, net of unearned discount	$ 1,689,975	$ 1,679,961