Fair Value Measurements (Financial Assets and Financial Liabilities Measured at Fair Value) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	$ 202,735
Mortgage-backed securities available for sale	360,084	364,931
Level 3 Inputs | Items measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage-backed securities available for sale	360,084	364,931
Level 3 Inputs | Items measured on a recurring basis | U.S. agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	139,435	102,776
Level 3 Inputs | Items measured on a recurring basis | State and municipal obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	21,586	18,544
Level 3 Inputs | Items measured on a recurring basis | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	41,714	39,449
Level 3 Inputs | Items measured on a recurring basis | Equity investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,601	4,510
Level 3 Inputs | Items measured on a non-recurring basis | Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	3,628	1,513
Level 3 Inputs | Items measured on a non-recurring basis | Loans measured for impairment based on the fair value of underlying collateral
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	9,856	8,773
Level 1 Inputs | Items measured on a recurring basis | Equity investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	5,601	4,510
Level 2 Inputs | Items measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage-backed securities available for sale	360,084	364,931
Level 2 Inputs | Items measured on a recurring basis | U.S. agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	139,435	102,776
Level 2 Inputs | Items measured on a recurring basis | State and municipal obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	21,586	18,544
Level 2 Inputs | Items measured on a recurring basis | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	$ 41,714	$ 39,449