Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 225,248	$ 192,820
Gross Unrealized Gains	5,673	4,292
Gross Unrealized Losses	(724)	(1,248)
Total securities available for sale, Fair Value	230,197	195,864
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,690	37,406
Gross Unrealized Gains	158	117
Gross Unrealized Losses	(85)	(77)
Total securities available for sale, Fair Value	35,763	37,446
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	104,811	92,177
Gross Unrealized Gains	4,386	3,395
Gross Unrealized Losses	(255)	(574)
Total securities available for sale, Fair Value	108,942	94,998
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	84,266	62,756
Gross Unrealized Gains	853	483
Gross Unrealized Losses	(384)	(597)
Total securities available for sale, Fair Value	84,735	62,642
Total Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	224,767	192,339
Gross Unrealized Gains	5,397	3,995
Gross Unrealized Losses	(724)	(1,248)
Total securities available for sale, Fair Value	229,440	195,086
Equity Securities in Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	481	481
Gross Unrealized Gains	276	297
Total securities available for sale, Fair Value	$ 757	$ 778

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
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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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
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