Share-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation Expense	$ 97,000	$ 92,000
Related tax benefits on non-qualified stock options	$ 12,000	$ 4,000
Number of shares, stock options exercised	1,679
Restricted stock awards, continuous employment period from date of grant required for vesting of Plan	Three to five years