Loans and Leases - Summary of Current, Past Due and Nonaccrual Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 84,400,551	$ 64,785,780
30-89 Days past due	1,135,296	530,901
Accruing loans Past Due 90 Days or More	317,441	245,020
Purchased impaired	768,329	197,737
Nonaccrual	799,409	799,151
Loans and leases, net of unearned discount	87,489,499	66,668,956
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	20,122,648	19,228,265
30-89 Days past due	52,868	37,246
Accruing loans Past Due 90 Days or More	2,310	1,805
Purchased impaired	1,902	10,300
Nonaccrual	241,917	177,445
Loans and leases, net of unearned discount	20,422,338	19,461,292
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	23,645,354	22,208,491
30-89 Days past due	172,439	118,704
Accruing loans Past Due 90 Days or More	12,963	22,170
Purchased impaired	46,790	51,312
Nonaccrual	179,606	141,600
Loans and leases, net of unearned discount	24,065,942	22,556,939
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	1,507,856	1,273,607
30-89 Days past due	7,969	11,827
Accruing loans Past Due 90 Days or More	5,760	492
Purchased impaired	28,734	98,347
Nonaccrual	28,429	71,517
Loans and leases, net of unearned discount	1,585,673	1,465,140
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,428,939	3,484,932
30-89 Days past due	65,932	17,678
Accruing loans Past Due 90 Days or More	7,936
Purchased impaired	24,525	17,181
Nonaccrual	16,363	25,699
Loans and leases, net of unearned discount	3,545,696	3,545,490
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	20,507,551	7,640,368
30-89 Days past due	560,312	226,932
Accruing loans Past Due 90 Days or More	284,451	216,489
Purchased impaired	488,599	18,223
Nonaccrual	153,281	180,275
Loans and leases, net of unearned discount	22,010,273	8,318,013
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,885,073	249,810
30-89 Days past due	137,289	11,774
Purchased impaired	175,518
Nonaccrual	61,950	77,704
Loans and leases, net of unearned discount	4,259,830	339,288
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	5,805,222	5,859,378
30-89 Days past due	45,604	42,945
Purchased impaired	2,261	2,374
Nonaccrual	84,467	89,291
Loans and leases, net of unearned discount	5,952,776	6,021,884
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2,446,473	1,931,138
30-89 Days past due	56,181	30,500
Nonaccrual	16,597	17,578
Loans and leases, net of unearned discount	2,519,257	1,979,349
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	3,051,435	2,909,791
30-89 Days past due	36,702	33,295
Accruing loans Past Due 90 Days or More	4,021	4,064
Nonaccrual	16,799	18,042
Loans and leases, net of unearned discount	3,127,714	2,981,561
Accruing Loans Acquired at Discount [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	68,473	110,367
Accruing Loans Acquired at Discount [Member] | Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	693	6,231
Accruing Loans Acquired at Discount [Member] | Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	8,790	14,662
Accruing Loans Acquired at Discount [Member] | Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	6,925	9,350
Accruing Loans Acquired at Discount [Member] | Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	2,001
Accruing Loans Acquired at Discount [Member] | Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	16,079	35,726
Accruing Loans Acquired at Discount [Member] | Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	15,222	27,896
Accruing Loans Acquired at Discount [Member] | Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	6	133
Accruing Loans Acquired at Discount [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans Past Due 90 Days or More	$ 18,757	$ 16,369