Fair Value of Assets Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	$ 251,813	$ 214,393
Obligations of U. S. Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	32,527	36,359
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	110,367	98,910
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	81,032	61,967
Corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	26,918	16,187
Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	969	970
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	970
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	970
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Securities available-for-sale, at fair value	248,061	210,755
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	32,527	36,359
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	110,367	98,910
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	81,032	61,967
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	24,135	13,519
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	2,783	2,668
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	2,783	2,668
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