Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 87,999,720	$ 86,140,950
30-89 Days Past Due	1,174,132	866,337
Accruing Loans Past Due 90 Days or More	518,728	222,527
Purchased Impaired	227,545	303,305
Nonaccrual	963,112	893,608
Loans and leases, net of unearned discount	90,922,869	88,466,477
Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	39,632	39,750
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	23,290,797	22,701,020
30-89 Days Past Due	184,011	39,798
Accruing Loans Past Due 90 Days or More	16,776	2,567
Nonaccrual	346,557	234,423
Loans and leases, net of unearned discount	23,838,168	22,977,976
Commercial, Financial, Leasing, etc. [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	27	168
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	26,311,414	25,250,983
30-89 Days Past Due	165,579	134,474
Accruing Loans Past Due 90 Days or More	6,740	11,457
Purchased Impaired	15,601	9,769
Nonaccrual	158,474	203,672
Loans and leases, net of unearned discount	26,657,808	25,610,365
Commercial [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		10
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,521,315	1,665,178
30-89 Days Past Due	21,195	20,333
Purchased Impaired	753
Nonaccrual	3,982	4,798
Loans and leases, net of unearned discount	1,547,245	1,690,309
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	7,204,148	6,982,077
30-89 Days Past Due	95,346	43,615
Accruing Loans Past Due 90 Days or More	3,360	14,344
Purchased Impaired	1,237	641
Nonaccrual	32,770	22,205
Loans and leases, net of unearned discount	7,336,861	7,062,882
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	12,760,040	13,591,790
30-89 Days Past Due	451,274	404,808
Accruing Loans Past Due 90 Days or More	486,515	189,682
Purchased Impaired	143,145	203,044
Nonaccrual	235,663	233,352
Loans and leases, net of unearned discount	14,082,425	14,629,326
Residential [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	5,788	6,650
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,858,037	2,278,040
30-89 Days Past Due	65,215	72,544
Accruing Loans Past Due 90 Days or More	181
Purchased Impaired	66,809	89,851
Nonaccrual	83,427	84,685
Loans and leases, net of unearned discount	2,073,669	2,525,120
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,386,511	4,758,513
30-89 Days Past Due	30,229	25,416
Nonaccrual	63,215	71,292
Loans and leases, net of unearned discount	4,481,617	4,860,254
Home Equity Lines and Loans [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	1,662	5,033
Recreational Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	5,484,997	4,085,781
30-89 Days Past Due	36,827	29,947
Nonaccrual	14,219	11,199
Loans and leases, net of unearned discount	5,536,142	4,127,162
Recreational Finance [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	99	235
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,787,221	3,555,757
30-89 Days Past Due	78,478	79,804
Nonaccrual	21,293	23,359
Loans and leases, net of unearned discount	3,886,992	3,658,920
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,395,240	1,271,811
30-89 Days Past Due	45,978	15,598
Accruing Loans Past Due 90 Days or More	5,156	4,477
Nonaccrual	3,512	4,623
Loans and leases, net of unearned discount	1,481,942	1,324,163
Other [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	$ 32,056	$ 27,654