Investment Securities - Investment Securities Available-for-Sale and Held-to-Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	$ 207,134	$ 202,039
Available-for-Sale, Gross Unrealized Gains	3,122	3,306
Available-for-Sale, Gross Unrealized Losses	(466)	(379)
Available-for-Sale, Estimated Fair Value	209,790	204,966
Held-to-Maturity, Amortized Cost	40,074us-gaap_HeldToMaturitySecurities	29,120us-gaap_HeldToMaturitySecurities
Held-to-Maturity, Gross Unrealized Gains	88	88
Held-to-Maturity, Gross Unrealized Losses	(129)	(54)
Held-to-Maturity, Estimated Fair Value	40,033	29,154
Residential [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	136,318	139,980
Available-for-Sale, Gross Unrealized Gains	1,667	1,896
Available-for-Sale, Gross Unrealized Losses	(224)	(192)
Available-for-Sale, Estimated Fair Value	137,761	141,684
Commercial [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	48,525	35,873
Available-for-Sale, Gross Unrealized Gains	266	164
Available-for-Sale, Gross Unrealized Losses	(240)	(93)
Available-for-Sale, Estimated Fair Value	48,551	35,944
Held-to-Maturity, Amortized Cost	16,820	10,666
Held-to-Maturity, Gross Unrealized Gains	48	65
Held-to-Maturity, Gross Unrealized Losses	(74)	(2)
Held-to-Maturity, Estimated Fair Value	16,794	10,729
Obligations of States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	15,075	15,673
Available-for-Sale, Gross Unrealized Gains	1,165	1,241
Available-for-Sale, Estimated Fair Value	16,240	16,914
Held-to-Maturity, Amortized Cost	582	584
Held-to-Maturity, Gross Unrealized Gains		4
Held-to-Maturity, Estimated Fair Value	582	588
Obligations of U.S. Government Sponsored Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	6,338	6,360
Available-for-Sale, Gross Unrealized Gains	24	5
Available-for-Sale, Gross Unrealized Losses		(1)
Available-for-Sale, Estimated Fair Value	6,362	6,364
Held-to-Maturity, Amortized Cost	22,672	17,870
Held-to-Maturity, Gross Unrealized Gains	40	19
Held-to-Maturity, Gross Unrealized Losses	(55)	(52)
Held-to-Maturity, Estimated Fair Value	22,657	17,837
Corporate notes [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	798
Available-for-Sale, Gross Unrealized Losses	(2)
Available-for-Sale, Estimated Fair Value	796
U.S. Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale, Amortized Cost	80	4,153
Available-for-Sale, Gross Unrealized Losses		(93)
Available-for-Sale, Estimated Fair Value	$ 80	$ 4,060

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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