Loans and Leases and the Allowance for Credit Losses - Summary of Loan Grades (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 88,521,998	$ 87,489,499
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	21,469,242	20,422,338
Commercial, Financial, Leasing, etc. [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	20,409,928	19,442,183
Commercial, Financial, Leasing, etc. [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	818,630	738,238
Commercial, Financial, Leasing, etc. [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	240,684	241,917
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	23,754,899	23,532,261
Commercial [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	22,785,132	22,697,398
Commercial [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	797,097	655,257
Commercial [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	172,670	179,606
Residential Builder and Developer [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,883,958	1,585,673
Residential Builder and Developer [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	1,704,457	1,497,465
Residential Builder and Developer [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	155,238	59,779
Residential Builder and Developer [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	24,263	28,429
Other Commercial Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	5,072,373	4,079,377
Other Commercial Construction [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	4,847,810	3,834,137
Other Commercial Construction [Member] | Criticized Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	203,269	228,877
Other Commercial Construction [Member] | Criticized Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases, net of unearned discount	$ 21,294	$ 16,363