Stockholders' Equity - Summary of Activity Related to Options Granted (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of stock options outstanding, beginning balance	4,045,324	3,640,324
Number of stock options granted	252,000	446,000
Number of stock options exercised	(1,138,331)	(30,500)
Number of stock options forfeited	(14,000)	(10,500)
Number of stock options expired	0
Number of stock options outstanding, ending balance	3,144,993	4,045,324	3,640,324
Number of stock options exercisable	2,829,329
Weighted average exercise price, options outstanding, beginning balance	$ 1.85	$ 1.76
Number of stock options unvested ending balance	315,664
Weighted average exercise price, options granted	$ 3.80	$ 2.61
Weighted average exercise price, options exercised	$ 0.78	$ 2.67
Weighted average exercise price, options forfeited	$ 2.43	$ 2.35
Weighted average exercise price, options expired	$ 0	$ 0
Weighted average exercise price, options outstanding, ending balance	$ 2.39	$ 1.85	$ 1.76
Aggregate fair value, beginning balance	$ 7,483,849	$ 6,406,970
Weighted average exercise price, options exercisable	$ 2.29
Aggregate fair value, ending balance	7,516,533	7,483,849	6,406,970
Weighted average remaining contractual term, options outstanding	1 year 5 months 23 days	2 years 18 days	2 years 8 months 9 days
Aggregate fair value, exercisable	$ 6,479,163