Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 86,140,950	$ 85,325,604
30-89 Days Past Due	866,337	1,078,943
Accruing Loans Past Due 90 Days or More	222,527	244,405
Purchased Impaired	303,305	410,015
Nonaccrual	893,608	882,598
Loans and leases, net of unearned discount	88,466,477	87,988,983
Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	39,750	47,418
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	22,701,020	21,332,234
30-89 Days Past Due	39,798	167,756
Accruing Loans Past Due 90 Days or More	2,567	1,322
Purchased Impaired		21
Nonaccrual	234,423	240,991
Loans and leases, net of unearned discount	22,977,976	21,742,651
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	168	327
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	25,250,983	24,910,381
30-89 Days Past Due	134,474	166,305
Accruing Loans Past Due 90 Days or More	11,457	4,444
Purchased Impaired	9,769	16,815
Nonaccrual	203,672	184,982
Loans and leases, net of unearned discount	25,610,365	25,288,943
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	6,016
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,665,178	1,618,973
30-89 Days Past Due	20,333	5,159
Purchased Impaired		1,135
Nonaccrual	4,798	6,451
Loans and leases, net of unearned discount	1,690,309	1,631,718
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	6,982,077	6,407,451
30-89 Days Past Due	43,615	23,467
Accruing Loans Past Due 90 Days or More	14,344
Purchased Impaired	641	4,706
Nonaccrual	22,205	10,088
Loans and leases, net of unearned discount	7,062,882	6,445,712
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	13,591,790	15,376,759
30-89 Days Past Due	404,808	474,372
Accruing Loans Past Due 90 Days or More	189,682	233,437
Purchased Impaired	203,044	282,102
Nonaccrual	233,352	235,834
Loans and leases, net of unearned discount	14,629,326	16,610,086
Residential [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	6,650	7,582
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2,278,040	2,718,019
30-89 Days Past Due	72,544	83,898
Purchased Impaired	89,851	105,236
Nonaccrual	84,685	96,105
Loans and leases, net of unearned discount	2,525,120	3,003,258
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,758,513	5,171,345
30-89 Days Past Due	25,416	38,546
Nonaccrual	71,292	74,500
Loans and leases, net of unearned discount	4,860,254	5,293,782
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	5,033	9,391
Recreational Finance [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,085,781	3,229,570
30-89 Days Past Due	29,947	23,802
Nonaccrual	11,199	6,509
Loans and leases, net of unearned discount	4,127,162	3,260,427
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	235	546
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,555,757	3,441,371
30-89 Days Past Due	79,804	78,511
Nonaccrual	23,359	23,781
Loans and leases, net of unearned discount	3,658,920	3,543,663
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,271,811	1,119,501
30-89 Days Past Due	15,598	17,127
Accruing Loans Past Due 90 Days or More	4,477	5,202
Nonaccrual	4,623	3,357
Loans and leases, net of unearned discount	1,324,163	1,168,743
Other [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	$ 27,654	$ 23,556