Investment Securities - Investment Securities Available-for-Sale and Held-to-Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	$ 202,039	$ 134,908
Available-for-Sale, Gross Unrealized Gains	3,306	2,422
Available-for-Sale, Gross Unrealized Losses	(379)	(1,576)
Available-for-Sale, Estimated Fair Value	204,966	135,754
Held-to-Maturity, Amortized Cost	29,120us-gaap_HeldToMaturitySecurities	35,050us-gaap_HeldToMaturitySecurities
Held-to-Maturity, Gross Unrealized Gains	88
Held-to-Maturity, Gross Unrealized Losses	(54)
Held-to-Maturity, Estimated Fair Value	29,154
Commercial [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	35,873	30,677
Available-for-Sale, Gross Unrealized Gains	164	143
Available-for-Sale, Gross Unrealized Losses	(93)	(355)
Available-for-Sale, Estimated Fair Value	35,944	30,465
Held-to-Maturity, Amortized Cost	10,666
Held-to-Maturity, Gross Unrealized Gains	65
Held-to-Maturity, Gross Unrealized Losses	(2)
Held-to-Maturity, Estimated Fair Value	10,729
Obligations of U.S. Government Sponsored Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	6,360	1,000
Available-for-Sale, Gross Unrealized Gains	5	1
Available-for-Sale, Gross Unrealized Losses	(1)
Available-for-Sale, Estimated Fair Value	6,364	1,001
Held-to-Maturity, Amortized Cost	17,870	35,050
Held-to-Maturity, Gross Unrealized Gains	19
Held-to-Maturity, Gross Unrealized Losses	(52)	(1,685)
Held-to-Maturity, Estimated Fair Value	17,837	33,365
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	15,673	16,230
Available-for-Sale, Gross Unrealized Gains	1,241	799
Available-for-Sale, Gross Unrealized Losses		(2)
Available-for-Sale, Estimated Fair Value	16,914	17,027
Held-to-Maturity, Amortized Cost	584
Held-to-Maturity, Gross Unrealized Gains	4
Held-to-Maturity, Estimated Fair Value	588
Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	139,980	82,840
Available-for-Sale, Gross Unrealized Gains	1,896	1,479
Available-for-Sale, Gross Unrealized Losses	(192)	(885)
Available-for-Sale, Estimated Fair Value	141,684	83,434
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized Cost	4,153	4,161
Available-for-Sale, Gross Unrealized Losses	(93)	(334)
Available-for-Sale, Estimated Fair Value	$ 4,060	$ 3,827

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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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 after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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