Debt and Equity Securities - Summary of Debt and Equity Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	$ 335,801	$ 347,520
Available-for-sale, Gross Unrealized Gains	1,834	1,056
Available-for-sale, Gross Unrealized Losses	1,024	2,156
Available-for-sale, Estimated Market Value	336,611us-gaap_AvailableForSaleSecurities	346,420us-gaap_AvailableForSaleSecurities
Held-To-Maturity Securities, Amortized Cost	28,154	28,123
Held-To-Maturity Securities, Gross Unrealized Gains	392	465
Held-To-Maturity Securities, Gross Unrealized Losses	157	188
Held-To-Maturity Securities, Estimated Market Value	28,389	28,400
Government- Sponsored Enterprises (GSEs) Residential Mortgage Backed [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	165,971	170,802
Available-for-sale, Gross Unrealized Gains	1,132	731
Available-for-sale, Gross Unrealized Losses	234	464
Available-for-sale, Estimated Market Value	166,869	171,069
Held-To-Maturity Securities, Amortized Cost	7,351	7,398
Held-To-Maturity Securities, Gross Unrealized Gains	82	76
Held-To-Maturity Securities, Gross Unrealized Losses	113	147
Held-To-Maturity Securities, Estimated Market Value	7,320	7,327
Obligations of States and Political Subdivisions [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	13,957	14,324
Available-for-sale, Gross Unrealized Gains	84	98
Available-for-sale, Gross Unrealized Losses	117	158
Available-for-sale, Estimated Market Value	13,924	14,264
Held-To-Maturity Securities, Amortized Cost	20,803	20,725
Held-To-Maturity Securities, Gross Unrealized Gains	310	389
Held-To-Maturity Securities, Gross Unrealized Losses	44	41
Held-To-Maturity Securities, Estimated Market Value	21,069	21,073
US Government-Sponsored Enterprises (GSEs) [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	126,302	131,767
Available-for-sale, Gross Unrealized Gains	338	129
Available-for-sale, Gross Unrealized Losses	623	1,329
Available-for-sale, Estimated Market Value	126,017	130,567
SBAP [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	29,571	30,627
Available-for-sale, Gross Unrealized Gains	280	98
Available-for-sale, Gross Unrealized Losses	50	205
Available-for-sale, Estimated Market Value	$ 29,801	$ 30,520

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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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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This item represents the cost of debt and equity 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 of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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

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Fair value of investments in debt securities classified as held-to-maturity.

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