Share-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Share-Based Compensation Expense	$ 42,000	$ 59,000	$ 144,000	$ 440,000
Amount of tax benefits	$ 18,000	$ 25,000	$ 61,000	$ 185,000
Number of options exercised