Stock-Based Compensation - Schedule of Stock Options Activity (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning outstanding balance	3,155,631	3,267,838
Granted	1,036,900	425,150
Exercised	(943,609)	(231,403)
Forfeited and cancelled	(23,718)	(305,954)
Ending outstanding balance	3,225,204	3,155,631
Aggregate intrinsic value of options exercised	$ 5,694,000	$ 443,000
Weighted average fair value of options granted	$ 5.61	$ 3.35