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Securities - Summary of Amortized Costs and Fair Values of Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Debt and Equity, Amortized Cost Basis, Total	$ 86,881	$ 105,851
Securities available for sale, Gross Unrealized Gains	1,504	601
Securities available for sale, Gross Unrealized (Losses)	(62)	(893)
Securities available for sale, Fair Value	88,323	105,559	[1]
Securities held to maturity, Amortized Cost	55,263	66,519
Securities held to maturity, Gross Unrealized Gains	1,042	264
Securities held to maturity, Gross Unrealized (Losses)		(345)
Securities held to maturity, Fair Value	56,305	66,438	[1]
Total securities, Amortized Cost	142,144	172,370
Total securities, Gross Unrealized Gains	2,546	865
Total securities, Gross Unrealized (Losses)	(62)	(1,238)
Total securities, Fair Value	144,628	171,997
U.S. Agency and Mortgage-Backed Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Debt and Equity, Amortized Cost Basis, Total	74,732	89,919
Securities available for sale, Gross Unrealized Gains	1,092	261
Securities available for sale, Gross Unrealized (Losses)	(62)	(843)
Securities available for sale, Fair Value	75,762	89,337
Securities held to maturity, Amortized Cost	39,118	49,662
Securities held to maturity, Gross Unrealized Gains	487	36
Securities held to maturity, Gross Unrealized (Losses)		(326)
Securities held to maturity, Fair Value	39,605	49,372
Obligations of States and Political Subdivisions [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Debt and Equity, Amortized Cost Basis, Total	12,148	15,931
Securities available for sale, Gross Unrealized Gains	402	333
Securities available for sale, Gross Unrealized (Losses)		(50)
Securities available for sale, Fair Value	12,550	16,214
Securities held to maturity, Amortized Cost	14,645	15,357
Securities held to maturity, Gross Unrealized Gains	531	228
Securities held to maturity, Gross Unrealized (Losses)		(19)
Securities held to maturity, Fair Value	15,176	15,566
Corporate Equity Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Debt and Equity, Amortized Cost Basis, Total	1	1
Securities available for sale, Gross Unrealized Gains	10	7
Securities available for sale, Fair Value	11	8
Corporate Debt Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Securities held to maturity, Amortized Cost	1,500	1,500
Securities held to maturity, Gross Unrealized Gains	24
Securities held to maturity, Fair Value	$ 1,524	$ 1,500
[1] Derived from audited consolidated financial statements.

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