Loans - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Receivables [Abstract]
Minimum percentage of concentrations of loans	10.00%		10.00%
Concentrations of loans	$ 0		$ 0
Allowance for loan losses	9,399,000	10,600,000	10,648,000
Ratio of the allowance for loan losses to total loans	1.75%	1.92%	1.99%
Company's annualized net charge off ratios	0.77%	0.71%	0.52%
Ratios of allowance for loan losses to non-accrual loans	79.60%	87.23%	138.99%
Annual reviews of loan to ascertain the borrowers continued ability to service	1,000,000
Loans past due period for classify to risk grade	60 days
Loans past due period for classify to substandard grade	12 months
Company's impaired loans	40,444,000	90,400,000	66,604,000
Related Allowance	$ 3,549,000	$ 3,700,000	$ 3,841,000