Loans and Allowance for Loan Losses - Activity in All by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				$ 40,889				$ 39,034	$ 40,889	$ 39,034
Charge- offs									(7,325)	(2,619)
Recoveries									427	1,402
Net charge- offs									(6,898)	(1,217)
Provisions charged to operations	$ 3,646	$ 1,424	$ 1,271	1,334	$ 1,840	$ (3,115)	$ 3,129	1,218	7,675	3,072	$ 1,258
Balance at end of period	41,666				40,889				41,666	40,889	39,034
Non-residential Real Estate Owner Occupied [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				4,406				4,827	4,406	4,827
Charge- offs									(37)	(42)
Recoveries									1	102
Net charge- offs									(36)	60
Provisions charged to operations									291	(481)
Balance at end of period	4,661				4,406				4,661	4,406	4,827
Non-residential Real Estate Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				9,616				11,026	9,616	11,026
Charge- offs									(708)	(29)
Recoveries									2	49
Net charge- offs									(706)	20
Provisions charged to operations									1,011	(1,430)
Balance at end of period	9,921				9,616				9,921	9,616	11,026
Residential Real Estate Permanent Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				2,948				2,825	2,948	2,825
Charge- offs									(222)	(207)
Recoveries									40	78
Net charge- offs									(182)	(129)
Provisions charged to operations									382	252
Balance at end of period	3,148				2,948				3,148	2,948	2,825
Residential Real Estate All Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				6,269				6,708	6,269	6,708
Charge- offs									(138)	(171)
Recoveries									17	32
Net charge- offs									(121)	(139)
Provisions charged to operations									577	(300)
Balance at end of period	6,725				6,269				6,725	6,269	6,708
Non-consumer Non-real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				12,771				8,977	12,771	8,977
Charge- offs									(3,799)	(564)
Recoveries									199	70
Net charge- offs									(3,600)	(494)
Provisions charged to operations									2,583	4,288
Balance at end of period	11,754				12,771				11,754	12,771	8,977
Consumer Non-real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				2,404				2,556	2,404	2,556
Charge- offs									(626)	(687)
Recoveries									124	203
Net charge- offs									(502)	(484)
Provisions charged to operations									740	332
Balance at end of period	2,642				2,404				2,642	2,404	2,556
Other Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				2,359				1,991	2,359	1,991
Charge- offs									(1,109)	(351)
Recoveries									16	149
Net charge- offs									(1,093)	(202)
Provisions charged to operations									1,382	570
Balance at end of period	2,648				2,359				2,648	2,359	1,991
Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period				$ 116				$ 124	116	124
Charge- offs									(686)	(568)
Recoveries									28	719
Net charge- offs									(658)	151
Provisions charged to operations									709	(159)
Balance at end of period	$ 167				$ 116				$ 167	$ 116	$ 124