Debt and Equity Securities - Summary of Debt and Equity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	$ 329,655	$ 347,520
Available-for-sale, Gross Unrealized Gains	847	1,056
Available-for-sale, Gross Unrealized Losses	2,018	2,156
Available-for-sale, Estimated Market Value	328,484	346,420
Held-To-Maturity Securities, Amortized Cost	26,204	28,123
Held-To-Maturity Securities, Gross Unrealized Gains	325	465
Held-To-Maturity Securities, Gross Unrealized Losses	278	188
Held-To-Maturity Securities, Estimated Market Value	26,251	28,400
Government- Sponsored Enterprises (GSEs) Residential Mortgage Backed [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	163,538	170,802
Available-for-sale, Gross Unrealized Gains	477	731
Available-for-sale, Gross Unrealized Losses	857	464
Available-for-sale, Estimated Market Value	163,158	171,069
Held-To-Maturity Securities, Amortized Cost	7,189	7,398
Held-To-Maturity Securities, Gross Unrealized Gains	67	76
Held-To-Maturity Securities, Gross Unrealized Losses	191	147
Held-To-Maturity Securities, Estimated Market Value	7,065	7,327
Obligations of States and Political Subdivisions [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	23,279	14,324
Available-for-sale, Gross Unrealized Gains	37	98
Available-for-sale, Gross Unrealized Losses	252	158
Available-for-sale, Estimated Market Value	23,064	14,264
Held-To-Maturity Securities, Amortized Cost	19,015	20,725
Held-To-Maturity Securities, Gross Unrealized Gains	258	389
Held-To-Maturity Securities, Gross Unrealized Losses	87	41
Held-To-Maturity Securities, Estimated Market Value	19,186	21,073
US Government-Sponsored Enterprises (GSEs) and Agency-Backed Securities [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	113,691	131,767
Available-for-sale, Gross Unrealized Gains	241	129
Available-for-sale, Gross Unrealized Losses	787	1,329
Available-for-sale, Estimated Market Value	113,145	130,567
SBAP [Member]
Summary Of Debt And Equity Securities [Line Items]
Available-for-sale, Amortized Cost	29,147	30,627
Available-for-sale, Gross Unrealized Gains	92	98
Available-for-sale, Gross Unrealized Losses	122	205
Available-for-sale, Estimated Market Value	$ 29,117	$ 30,520