Loans - Loans, Excluding Purchased Credit-Impaired Loans by Internal Ratings (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 5,634,957	$ 5,632,716
Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,218,177	1,237,137
Total commercial real estate | Non-owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	850,766	866,392
Total commercial real estate | Other commercial construction and land
Financing Receivable, Recorded Investment [Line Items]
Total loans	194,971	196,795
Total commercial real estate | Multifamily commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	75,737	80,708
Total commercial real estate | 1-4 family residential construction and land
Financing Receivable, Recorded Investment [Line Items]
Total loans	96,703	93,242
Total commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,471,781	2,415,932
Total commercial | Owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,095,460	1,104,972
Total commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,375,233	1,309,704
Total commercial | Lease financing
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,088	1,256
Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,785,552	1,829,545
Total consumer | 1-4 family residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,015,071	1,017,791
Total consumer | Home equity loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	368,510	375,276
Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	401,971	436,478
Other
Financing Receivable, Recorded Investment [Line Items]
Total loans	159,447	150,102
Non-PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,626,540	4,565,408
Non-PCI Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,580,885	4,519,494
Non-PCI Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	11,151	21,788
Non-PCI Loans | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,978	15,181
Non-PCI Loans | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,526	8,945
Non-PCI Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	836,744	821,961
Non-PCI Loans | Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	832,836	817,953
Non-PCI Loans | Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,147	1,154
Non-PCI Loans | Total commercial real estate | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,277	1,174
Non-PCI Loans | Total commercial real estate | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,484	1,680
Non-PCI Loans | Total commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	570,425	563,640
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	568,064	561,080
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,147	1,154
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,214	1,406
Non-PCI Loans | Total commercial real estate | Non-owner occupied commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Other commercial construction and land
Financing Receivable, Recorded Investment [Line Items]
Total loans	118,469	110,918
Non-PCI Loans | Total commercial real estate | Other commercial construction and land | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	118,263	110,710
Non-PCI Loans | Total commercial real estate | Other commercial construction and land | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Other commercial construction and land | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	20	22
Non-PCI Loans | Total commercial real estate | Other commercial construction and land | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	186	186
Non-PCI Loans | Total commercial real estate | Other commercial construction and land | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	53,989	57,099
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	53,905	57,011
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	84	88
Non-PCI Loans | Total commercial real estate | Multifamily commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land
Financing Receivable, Recorded Investment [Line Items]
Total loans	93,861	90,304
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	92,604	89,152
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,257	1,152
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial real estate | 1-4 family residential construction and land | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,189,729	2,124,826
Non-PCI Loans | Total commercial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,157,095	2,092,365
Non-PCI Loans | Total commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,847	20,453
Non-PCI Loans | Total commercial | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	20,697	9,978
Non-PCI Loans | Total commercial | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,090	2,030
Non-PCI Loans | Total commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total loans	892,005	894,995
Non-PCI Loans | Total commercial | Owner occupied commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	875,206	880,806
Non-PCI Loans | Total commercial | Owner occupied commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	9,588	6,843
Non-PCI Loans | Total commercial | Owner occupied commercial real estate | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,072	6,239
Non-PCI Loans | Total commercial | Owner occupied commercial real estate | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,139	1,107
Non-PCI Loans | Total commercial | Owner occupied commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,296,636	1,228,575
Non-PCI Loans | Total commercial | Commercial and industrial loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,280,801	1,210,303
Non-PCI Loans | Total commercial | Commercial and industrial loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	259	13,610
Non-PCI Loans | Total commercial | Commercial and industrial loans | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	14,625	3,739
Non-PCI Loans | Total commercial | Commercial and industrial loans | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	951	923
Non-PCI Loans | Total commercial | Commercial and industrial loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Lease financing
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,088	1,256
Non-PCI Loans | Total commercial | Lease financing | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,088	1,256
Non-PCI Loans | Total commercial | Lease financing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Lease financing | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Lease financing | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total commercial | Lease financing | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,473,227	1,501,357
Non-PCI Loans | Total consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,464,114	1,491,912
Non-PCI Loans | Total consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	157	181
Non-PCI Loans | Total consumer | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,004	4,029
Non-PCI Loans | Total consumer | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,952	5,235
Non-PCI Loans | Total consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer | 1-4 family residential
Financing Receivable, Recorded Investment [Line Items]
Total loans	778,463	767,808
Non-PCI Loans | Total consumer | 1-4 family residential | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	775,187	764,302
Non-PCI Loans | Total consumer | 1-4 family residential | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	103	126
Non-PCI Loans | Total consumer | 1-4 family residential | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,165	2,160
Non-PCI Loans | Total consumer | 1-4 family residential | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,008	1,220
Non-PCI Loans | Total consumer | 1-4 family residential | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer | Home equity loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	295,549	300,292
Non-PCI Loans | Total consumer | Home equity loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	291,460	295,726
Non-PCI Loans | Total consumer | Home equity loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	54	55
Non-PCI Loans | Total consumer | Home equity loans | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,839	1,869
Non-PCI Loans | Total consumer | Home equity loans | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,196	2,642
Non-PCI Loans | Total consumer | Home equity loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total loans	399,215	433,257
Non-PCI Loans | Total consumer | Other consumer loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	397,467	431,884
Non-PCI Loans | Total consumer | Other consumer loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer | Other consumer loans | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Total consumer | Other consumer loans | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,748	1,373
Non-PCI Loans | Total consumer | Other consumer loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Other
Financing Receivable, Recorded Investment [Line Items]
Total loans	126,840	117,264
Non-PCI Loans | Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans	126,840	117,264
Non-PCI Loans | Other | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Other | Substandard Accruing/Accreting
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Other | Substandard Nonaccrual
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Non-PCI Loans | Other | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 0	$ 0