Stock-Based Compensation - Schedule of Standard and Market-based Stock Options Activity (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Standard Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Beginning outstanding balance	3,486,157	3,227,167
Granted	491,520	604,620
Exercised	(214,466)	(205,744)
Forfeited	(109,222)	(102,454)
Expired	(49,920)	(37,432)
Ending outstanding balance	3,604,069	3,486,157
Aggregate intrinsic value of options exercised (in dollars)	$ 1,045,000	$ 1,125,000
Weighted average fair value of options granted (in dollars per share)	$ 4.50	$ 4.93
Market Condition Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Beginning outstanding balance	50,000	0
Granted	150,000	50,000
Exercised	0	0
Forfeited and cancelled	0	0
Ending outstanding balance	200,000	50,000
Aggregate intrinsic value of options exercised (in dollars)	$ 0	$ 0
Weighted average fair value of options granted (in dollars per share)	$ 3.64	$ 5.71