Loans and Allowance for Loan Losses - Activity in All by Class of Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	$ 44,571	$ 41,557	$ 41,666	$ 40,889
Charge- offs	(929)	(266)	(2,209)	(1,028)
Recoveries	120	59	202	155
Net charge- offs	(809)	(207)	(2,007)	(873)
Provisions charged to operations	2,804	1,271	6,907	2,605
Balance at end of period	46,566	42,621	46,566	42,621
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	4,832	4,461	4,661	4,406
Charge- offs	(9)		(10)	(1)
Recoveries				1
Net charge- offs	(9)		(10)
Provisions charged to operations	73	42	245	97
Balance at end of period	4,896	4,503	4,896	4,503
Real Estate [Member] | Non-residential Real Estate Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	10,211	9,898	9,921	9,616
Charge- offs	(3)		(4)
Recoveries	1	1	2	1
Net charge- offs	(2)	1	(2)	1
Provisions charged to operations	93	(19)	383	263
Balance at end of period	10,302	9,880	10,302	9,880
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	3,164	2,984	3,148	2,948
Charge- offs	(49)	(56)	(99)	(96)
Recoveries	21	5	38	14
Net charge- offs	(28)	(51)	(61)	(82)
Provisions charged to operations	67	177	116	244
Balance at end of period	3,203	3,110	3,203	3,110
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	7,989	6,578	6,725	6,269
Charge- offs	(70)	(7)	(137)	(75)
Recoveries	7	4	11	9
Net charge- offs	(63)	(3)	(126)	(66)
Provisions charged to operations	367	(90)	1,694	282
Balance at end of period	8,293	6,485	8,293	6,485
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	12,813	13,068	11,754	12,771
Charge- offs	(502)	(16)	(1,305)	(169)
Recoveries	35	7	46	38
Net charge- offs	(467)	(9)	(1,259)	(131)
Provisions charged to operations	1,095	654	2,946	1,073
Balance at end of period	13,441	13,713	13,441	13,713
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,553	2,327	2,642	2,404
Charge- offs	(134)	(103)	(355)	(230)
Recoveries	38	40	76	55
Net charge- offs	(96)	(63)	(279)	(175)
Provisions charged to operations	292	235	386	270
Balance at end of period	2,749	2,499	2,749	2,499
Other Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	2,790	2,241	2,648	2,359
Charge- offs	(149)	(50)	(282)	(263)
Recoveries	7		13	9
Net charge- offs	(142)	(50)	(269)	(254)
Provisions charged to operations	729	240	998	326
Balance at end of period	3,377	2,431	3,377	2,431
Acquired Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Balance at beginning of period	219		167	116
Charge- offs	(13)	(34)	(17)	(194)
Recoveries	11	2	16	28
Net charge- offs	(2)	(32)	(1)	(166)
Provisions charged to operations	88	$ 32	139	$ 50
Balance at end of period	$ 305		$ 305