Commitments, Contingencies and Off-Balance-Sheet Risk - Contractual Amount of Financial Instruments with Off-Balance-Sheet Risk (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	$ 7,095	$ 9,723
Variable Rate	158,564	138,304
Lines of Credit and Construction Loans [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	6,755	9,378
Variable Rate	137,493	118,182
Overdraft Protection [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	46	51
Variable Rate	20,275	19,726
Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fixed Rate	294	294
Variable Rate	$ 796	$ 396