Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 85,325,604	$ 87,968,321
30-89 Days Past Due	1,078,943	1,025,245
Accruing Loans Past Due 90 Days or More	244,405	300,659
Purchased Impaired	410,015	578,032
Nonaccrual	882,598	920,015
Loans and leases, net of unearned discount	87,988,983	90,853,416
Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	47,418	61,144
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	21,332,234	22,287,857
30-89 Days Past Due	167,756	53,503
Accruing Loans Past Due 90 Days or More	1,322	6,195
Purchased Impaired	21	641
Nonaccrual	240,991	261,434
Loans and leases, net of unearned discount	21,742,651	22,610,047
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	327	417
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	24,910,381	25,076,684
30-89 Days Past Due	166,305	183,531
Accruing Loans Past Due 90 Days or More	4,444	7,054
Purchased Impaired	16,815	31,404
Nonaccrual	184,982	176,201
Loans and leases, net of unearned discount	25,288,943	25,487,744
Commercial [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	6,016	12,870
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,618,973	1,884,989
30-89 Days Past Due	5,159	4,667
Accruing Loans Past Due 90 Days or More		5
Purchased Impaired	1,135	14,006
Nonaccrual	6,451	16,707
Loans and leases, net of unearned discount	1,631,718	1,922,326
Residential Builder and Developer [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		1,952
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	6,407,451	5,985,118
30-89 Days Past Due	23,467	77,701
Accruing Loans Past Due 90 Days or More		922
Purchased Impaired	4,706	14,274
Nonaccrual	10,088	18,111
Loans and leases, net of unearned discount	6,445,712	6,096,324
Other Commercial Construction [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		198
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	15,376,759	17,631,377
30-89 Days Past Due	474,372	485,468
Accruing Loans Past Due 90 Days or More	233,437	281,298
Purchased Impaired	282,102	378,549
Nonaccrual	235,834	229,242
Loans and leases, net of unearned discount	16,610,086	19,017,471
Residential [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	7,582	11,537
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2,718,019	3,239,344
30-89 Days Past Due	83,898	88,366
Purchased Impaired	105,236	139,158
Nonaccrual	96,105	106,573
Loans and leases, net of unearned discount	3,003,258	3,573,441
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	5,171,345	5,502,091
30-89 Days Past Due	38,546	44,565
Nonaccrual	74,500	81,815
Loans and leases, net of unearned discount	5,293,782	5,641,149
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	9,391	12,678
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,441,371	2,869,232
30-89 Days Past Due	78,511	56,158
Nonaccrual	23,781	18,674
Loans and leases, net of unearned discount	3,543,663	2,944,065
Automobile [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More		1
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	4,349,071	3,491,629
30-89 Days Past Due	40,929	31,286
Accruing Loans Past Due 90 Days or More	5,202	5,185
Nonaccrual	9,866	11,258
Loans and leases, net of unearned discount	4,429,170	3,560,849
Other [Member] | Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing Loans Past Due 90 Days or More	$ 24,102	$ 21,491