Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 447,909	$ 493,691
Unrealized Gains	7,784	7,683
Unrealized Losses	(2,628)	(5,539)
Fair Value	453,065	495,835
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	127,616	139,823
Unrealized Gains	1,034	1,107
Unrealized Losses	(174)	(579)
Fair Value	128,476	140,351
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	143,886	153,492
Unrealized Gains	5,444	4,194
Unrealized Losses	(279)	(649)
Fair Value	149,051	157,037
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	117,039	136,807
Unrealized Gains	774	551
Unrealized Losses	(1,032)	(2,382)
Fair Value	116,781	134,976
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,612	18,299
Unrealized Gains	108	77
Unrealized Losses	(500)	(962)
Fair Value	18,220	17,414
Pooled Trust Preferred [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	800
Unrealized Gains	0	1,249
Unrealized Losses	0	0
Fair Value	0	2,049
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	39,736	43,450
Unrealized Gains	424	505
Unrealized Losses	(595)	(918)
Fair Value	39,565	43,037
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,020	1,020
Unrealized Gains	0	0
Unrealized Losses	(48)	(49)
Fair Value	$ 972	$ 971