Share-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation [Abstract]
Stock-based compensation expense under share based plans	$ 336,000	$ 298,000	$ 1,174,000	$ 1,005,000
Cash received from employee stock purchase plan	377,000	230,000	793,000	470,000
Unrecognized compensation expense related to unvested portion of all share-based compensation	$ 1,900,000		$ 1,900,000
Expected weighted average recognition period for unrecognized compensation expense			1 year 2 months 12 days