Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Receivables [Abstract]
Total loans	$ 1,075,487,000	$ 1,035,288,000	$ 1,075,487,000	$ 1,035,288,000	$ 1,041,189,000
Amount of increase in total loans			34,300,000
Percentage increase in total loans			3.30%
Interest income recognized on impaired loans	$ 700,000	$ 400,000	$ 2,200,000	$ 1,100,000
Number of past due days for loans modified as TDR	30 days	30 days	30 days	30 days