Allowance for Credit Losses - Summary of Loan Grades (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 90,853,416	$ 87,489,499
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	22,610,047	20,422,338
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	21,398,581	19,442,183
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	950,032	738,238
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	261,434	241,917
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	25,487,744	23,532,261
Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	24,570,269	22,697,398
Commercial [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	741,274	655,257
Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	176,201	179,606
Residential Builder and Developer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,922,326	1,585,673
Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,789,071	1,497,465
Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	116,548	59,779
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	16,707	28,429
Other Commercial Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	6,096,324	4,079,377
Other Commercial Construction [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	5,912,351	3,834,137
Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	165,862	228,877
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 18,111	$ 16,363