Stock Option Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012 OptionPlan	Dec. 31, 2011	Dec. 31, 2010
Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]
Shares authorized to grant options	934,702
Stock option plans	2
Options exercised	67,916	2,832	0
Weighted-average grant-date fair value of options granted	$ 2.01	$ 1.33
Authorized but unissued shares	934,702
Shares remaining to be granted under plan	62,003
Unrecognized compensation cost related to nonvested share-based compensation arrangements granted	$ 31,000
Unrecognized compensation cost related to nonvested share-based compensation arrangements granted, expected to be recognized weighted-average period	1 year
Cash received from options exercised under all share-based payment arrangements	551,000	17,000	0
Options exercised during the period, intrinsic value	$ 287,000	$ 7,000