Summary of Status of Company's Stock Option Plan (Detail) (Stock Option Plan, USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Stock Option Plan
Shares
Outstanding at beginning of period	3,348,935	3,435,443	3,435,443
Cancelled	(8,617)		(8,313)
Exercised	(945,761)		(109,038)
Granted	110,000	30,843	30,843
Outstanding at end of period	2,504,557		3,348,935
Weighted Average Exercise Price
Outstanding at beginning of period	$ 1.23	$ 1.22	$ 1.22
Cancelled	$ 1.10		$ 1.10
Exercised	$ 1.20		$ 1.42
Granted	$ 3.01		$ 3.27
Outstanding at end of period	$ 1.33		$ 1.23