Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				$ 41,710				$ 44,654	$ 41,710	$ 44,654	$ 47,368
Allowance for loan commitments, beginning balance				613				455	613	455	602
Total beginning allowance for credit losses				42,323				45,109	42,323	45,109	47,970
Provision for loan losses									8,520	8,195	6,552
Provision for loan commitments									(42)	158	(147)
Total provision for credit losses	$ 2,128	$ 2,214	$ 1,811	2,324	$ 2,585	$ 1,798	$ 2,681	1,289	8,478	8,353	6,405
Charge-offs									(10,853)	(14,743)	(12,899)
Recoveries									4,297	3,604	3,633
Net charge-offs									(6,556)	(11,139)	(9,266)
Allowance for loan losses, ending balance	43,674				41,710				43,674	41,710	44,654
Allowance for loan commitments, ending balance	571				613				571	613	455
Total ending allowance for credit losses	44,245				42,323				44,245	42,323	45,109
Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				4,390				5,654	4,390	5,654	6,056
Allowance for loan commitments, beginning balance				157				194	157	194	301
Total beginning allowance for credit losses				4,547				5,848	4,547	5,848	6,357
Provision for loan losses									26	(1,265)	(402)
Provision for loan commitments									(6)	(37)	(107)
Total provision for credit losses									20	(1,302)	(509)
Charge-offs									(73)
Recoveries									5	1
Net charge-offs									(68)	1
Allowance for loan losses, ending balance	4,348				4,390				4,348	4,390	5,654
Allowance for loan commitments, ending balance	151				157				151	157	194
Total ending allowance for credit losses	4,499				4,547				4,499	4,547	5,848
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				14,748				17,573	14,748	17,573	18,157
Allowance for loan commitments, beginning balance				26				10	26	10	62
Total beginning allowance for credit losses				14,774				17,583	14,774	17,583	18,219
Provision for loan losses									4,223	1,250	1,239
Provision for loan commitments									(9)	16	(52)
Total provision for credit losses									4,214	1,266	1,187
Charge-offs									(1,886)	(4,915)	(2,426)
Recoveries									1,543	840	603
Net charge-offs									(343)	(4,075)	(1,823)
Allowance for loan losses, ending balance	18,628				14,748				18,628	14,748	17,573
Allowance for loan commitments, ending balance	17				26				17	26	10
Total ending allowance for credit losses	18,645				14,774				18,645	14,774	17,583
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				10,002				9,063	10,002	9,063	9,925
Allowance for loan commitments, beginning balance				260				112	260	112	130
Total beginning allowance for credit losses				10,262				9,175	10,262	9,175	10,055
Provision for loan losses									1,160	3,289	1,429
Provision for loan commitments									(72)	148	(18)
Total provision for credit losses									1,088	3,437	1,411
Charge-offs									(3,070)	(2,785)	(3,485)
Recoveries									320	435	1,194
Net charge-offs									(2,750)	(2,350)	(2,291)
Allowance for loan losses, ending balance	8,412				10,002				8,412	10,002	9,063
Allowance for loan commitments, ending balance	188				260				188	260	112
Total ending allowance for credit losses	8,600				10,262				8,600	10,262	9,175
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				342				575	342	575	520
Total beginning allowance for credit losses				342				575	342	575	520
Provision for loan losses									1,077	391	601
Total provision for credit losses									1,077	391	601
Charge-offs									(884)	(846)	(779)
Recoveries									225	222	233
Net charge-offs									(659)	(624)	(546)
Allowance for loan losses, ending balance	760				342				760	342	575
Total ending allowance for credit losses	760				342				760	342	575
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				4,582				5,382	4,582	5,382	5,673
Allowance for loan commitments, beginning balance				7				9	7	9	5
Total beginning allowance for credit losses				4,589				5,391	4,589	5,391	5,678
Provision for loan losses									16	399	1,692
Provision for loan commitments									2	(2)	4
Total provision for credit losses									18	397	1,696
Charge-offs									(937)	(1,803)	(2,437)
Recoveries									445	604	454
Net charge-offs									(492)	(1,199)	(1,983)
Allowance for loan losses, ending balance	4,106				4,582				4,106	4,582	5,382
Allowance for loan commitments, ending balance	9				7				9	7	9
Total ending allowance for credit losses	4,115				4,589				4,115	4,589	5,391
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				4,763				4,078	4,763	4,078	5,020
Allowance for loan commitments, beginning balance				46				40	46	40	19
Total beginning allowance for credit losses				4,809				4,118	4,809	4,118	5,039
Provision for loan losses									1,356	2,337	1,144
Provision for loan commitments									(2)	6	21
Total provision for credit losses									1,354	2,343	1,165
Charge-offs									(3,606)	(2,892)	(3,120)
Recoveries									1,485	1,240	1,034
Net charge-offs									(2,121)	(1,652)	(2,086)
Allowance for loan losses, ending balance	3,998				4,763				3,998	4,763	4,078
Allowance for loan commitments, ending balance	44				46				44	46	40
Total ending allowance for credit losses	4,042				4,809				4,042	4,809	4,118
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, beginning balance				2,883				2,329	2,883	2,329	2,017
Allowance for loan commitments, beginning balance				117				90	117	90	85
Total beginning allowance for credit losses				$ 3,000				$ 2,419	3,000	2,419	2,102
Provision for loan losses									662	1,794	849
Provision for loan commitments									45	27	5
Total provision for credit losses									707	1,821	854
Charge-offs									(397)	(1,502)	(652)
Recoveries									274	262	115
Net charge-offs									(123)	(1,240)	(537)
Allowance for loan losses, ending balance	3,422				2,883				3,422	2,883	2,329
Allowance for loan commitments, ending balance	162				117				162	117	90
Total ending allowance for credit losses	$ 3,584				$ 3,000				$ 3,584	$ 3,000	$ 2,419