Fair Value of Assets Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	$ 233,621	$ 212,529
Obligations of U.S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	46,712	43,673
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	99,783	94,259
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	64,557	59,330
Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	21,596	14,293
Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	973	974
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	973	974
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	973	974
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	229,717	209,303
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	46,712	43,673
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	99,783	94,259
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	64,557	59,330
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	18,665	12,041
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	2,931	2,252
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	$ 2,931	$ 2,252