Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 420,856	$ 493,691
Unrealized Gains	6,667	7,683
Unrealized Losses	(2,762)	(5,539)
Fair Value	424,761	495,835
U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	121,022	139,823
Unrealized Gains	780	1,107
Unrealized Losses	(206)	(579)
Fair Value	121,596	140,351
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	138,825	153,492
Unrealized Gains	4,911	4,194
Unrealized Losses	(266)	(649)
Fair Value	143,470	157,037
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	103,962	136,807
Unrealized Gains	485	551
Unrealized Losses	(1,194)	(2,382)
Fair Value	103,253	134,976
Corporate Notes and Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,610	18,299
Unrealized Gains	85	77
Unrealized Losses	(426)	(962)
Fair Value	17,269	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	38,417	43,450
Unrealized Gains	406	505
Unrealized Losses	(619)	(918)
Fair Value	38,204	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	(51)	(49)
Fair Value	$ 969	$ 971

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 50
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-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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