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Securities - Summary of Amortized Costs and Fair Values of Securities Available for Sale and Held to Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Available-for-sale Securities, Debt and Equity, Amortized Cost Basis, Total	$ 108,796	$ 83,494
Securities available for sale, Gross Unrealized Gains	883	704
Securities available for sale, Gross Unrealized (Losses)	(513)	(906)
Securities available for sale, Fair Value	109,166	83,292
Securities held to maturity, Amortized Cost	54,276
Securities held to maturity, Gross Unrealized Gains	192
Securities held to maturity, Gross Unrealized (Losses)	(165)
Securities held to maturity, Fair Value	54,303	0
Total securities, Amortized Cost	163,072
Total securities, Gross Unrealized Gains	1,075
Total securities, Gross Unrealized (Losses)	(678)
Total securities, Fair Value	163,469
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	92,758	67,462
Securities available for sale, Gross Unrealized Gains	568	374
Securities available for sale, Gross Unrealized (Losses)	(463)	(807)
Securities available for sale, Fair Value	92,863	67,029
Securities held to maturity, Amortized Cost	42,490
Securities held to maturity, Gross Unrealized Gains	137
Securities held to maturity, Gross Unrealized (Losses)	(124)
Securities held to maturity, Fair Value	42,503
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	16,037	16,031
Securities available for sale, Gross Unrealized Gains	308	325
Securities available for sale, Gross Unrealized (Losses)	(50)	(99)
Securities available for sale, Fair Value	16,295	16,257
Securities held to maturity, Amortized Cost	11,786
Securities held to maturity, Gross Unrealized Gains	55
Securities held to maturity, Gross Unrealized (Losses)	(41)
Securities held to maturity, Fair Value	11,800
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	7	5
Securities available for sale, Fair Value	$ 8	$ 6

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