Allowance for Loan Losses - Presentation of Credit Quality Indicators (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	$ 2,759,593	$ 2,522,937	$ 2,282,524
Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,356,327	1,988,745
PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	378,222	493,988
PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	25,044	40,204
Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,305,293	1,918,006
Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	360,043	472,952
Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	27,571	17,646
Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	8,549	11,994
Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	23,463	53,093
Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	9,630	9,042
Mortgage Loans on Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,057,824	1,811,832
Mortgage Loans on Real Estate [Member] | Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	309,907	314,265	279,420
Mortgage Loans on Real Estate [Member] | Residential [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	229,609	207,585
Mortgage Loans on Real Estate [Member] | Residential [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	78,935	104,535
Mortgage Loans on Real Estate [Member] | Residential [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,363	2,145
Mortgage Loans on Real Estate [Member] | Residential [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	224,988	199,837
Mortgage Loans on Real Estate [Member] | Residential [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	75,600	102,895
Mortgage Loans on Real Estate [Member] | Residential [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,225	2,018
Mortgage Loans on Real Estate [Member] | Residential [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,849	600
Mortgage Loans on Real Estate [Member] | Residential [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,396	5,730
Mortgage Loans on Real Estate [Member] | Residential [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,486	1,040
Mortgage Loans on Real Estate [Member] | Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,747,917	1,497,567	1,335,939
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,484,420	1,163,643
Mortgage Loans on Real Estate [Member] | Commercial [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	250,037	310,864
Mortgage Loans on Real Estate [Member] | Commercial [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	13,460	23,060
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,457,128	1,118,868
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	236,740	293,935
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	15,108	10,321
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	6,057	10,795
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	12,184	34,454
Mortgage Loans on Real Estate [Member] | Commercial [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	7,240	6,134
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	362,303	395,283
Consumer [Member] | Home Equity Lines of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	289,715	322,492	352,584
Consumer [Member] | Home Equity Lines of Credit [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	263,590	285,419
Consumer [Member] | Home Equity Lines of Credit [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	21,765	29,335
Consumer [Member] | Home Equity Lines of Credit [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	4,360	7,738
Consumer [Member] | Home Equity Lines of Credit [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	258,024	275,251
Consumer [Member] | Home Equity Lines of Credit [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	20,442	27,378
Consumer [Member] | Home Equity Lines of Credit [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,518	2,494
Consumer [Member] | Home Equity Lines of Credit [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	509	445
Consumer [Member] | Home Equity Lines of Credit [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	3,048	7,674
Consumer [Member] | Home Equity Lines of Credit [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	814	1,512
Consumer [Member] | Home Equity Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	41,822	40,362	31,314
Consumer [Member] | Home Equity Loans [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	37,074	34,717
Consumer [Member] | Home Equity Loans [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	3,618	4,018
Consumer [Member] | Home Equity Loans [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,130	1,627
Consumer [Member] | Home Equity Loans [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	34,299	31,427
Consumer [Member] | Home Equity Loans [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	3,492	3,789
Consumer [Member] | Home Equity Loans [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	891	1,027
Consumer [Member] | Home Equity Loans [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	41	80
Consumer [Member] | Home Equity Loans [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1,884	2,263
Consumer [Member] | Home Equity Loans [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	85	149
Consumer [Member] | Other Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	30,766	32,429	33,074
Consumer [Member] | Other Consumer [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	28,167	28,998
Consumer [Member] | Other Consumer [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,534	3,367
Consumer [Member] | Other Consumer [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	65	64
Consumer [Member] | Other Consumer [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	27,542	28,339
Consumer [Member] | Other Consumer [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	2,437	3,164
Consumer [Member] | Other Consumer [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	385	415
Consumer [Member] | Other Consumer [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	92	74
Consumer [Member] | Other Consumer [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	240	244
Consumer [Member] | Other Consumer [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	5	129
Consumer and Industrial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	217,047	194,913	174,945
Consumer and Industrial [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	200,735	170,320
Consumer and Industrial [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	12,321	19,744
Consumer and Industrial [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	3,991	4,849
Consumer and Industrial [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	190,902	166,559
Consumer and Industrial [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	12,320	19,666
Consumer and Industrial [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	6,133	1,037
Consumer and Industrial [Member] | Special Mention [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	1
Consumer and Industrial [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	3,700	2,724
Consumer and Industrial [Member] | Substandard [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts		78
Construction [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	122,419	120,909
Construction [Member] | Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	55,429	46,135	38,618
Construction [Member] | Residential [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	54,613	31,778
Construction [Member] | Residential [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	141	13,636
Construction [Member] | Residential [Member] | PCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	675	721
Construction [Member] | Residential [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	54,602	31,440
Construction [Member] | Residential [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	141	13,636
Construction [Member] | Residential [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts		334
Construction [Member] | Residential [Member] | Substandard [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	11	4
Construction [Member] | Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	66,990	74,774	$ 36,518
Construction [Member] | Commercial [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	58,119	66,285
Construction [Member] | Commercial [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	8,871	8,489
Construction [Member] | Commercial [Member] | Pass [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	57,808	66,285
Construction [Member] | Commercial [Member] | Pass [Member] | PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	8,871	$ 8,489
Construction [Member] | Commercial [Member] | Special Mention [Member] | Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total loans, net of unamortized deferred loan fees and discounts	$ 311