Fair Value of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on a Non-recurring Basis (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Impaired loans, net of reserve	$ 3,549	$ 3,841	$ 3,700
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Impaired loans, net of reserve	$ 3,549	$ 3,841