Fair Value of Assets Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	$ 246,842	$ 254,746
Obligations of U. S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	21,904	27,372
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	101,437	104,582
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	93,692	93,036
Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	28,840	28,784
Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	969	972
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	969	972
Quoted Prices in Active Markets for Identical Assets (Level 1) | Obligations of U. S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	969	972
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	243,057	250,973
Significant Other Observable Inputs (Level 2) | Obligations of U. S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	21,904	27,372
Significant Other Observable Inputs (Level 2) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	101,437	104,582
Significant Other Observable Inputs (Level 2) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	93,692	93,036
Significant Other Observable Inputs (Level 2) | Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	26,024	25,983
Significant Other Observable Inputs (Level 2) | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	2,816	2,801
Significant Unobservable Inputs (Level 3) | Obligations of U. S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) | Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	2,816	2,801
Significant Unobservable Inputs (Level 3) | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	$ 0	$ 0