Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of stock options, Outstanding, balance	12,795,000
Number of stock options, Granted	3,207,000
Number stock options, Exercised	(1,332,000)
Number of stock options, Cancelled/Forfeited	(1,315,000)
Number of stock options, Outstanding, Balance	13,355,000	12,795,000
Number of stock options, Options vested and exercisable	6,927,000
Weighted-average exercise price, Outstanding, Balance	$ 5.89
Weighted-average exercise price, Granted	5.69
Weighted-average exercise price, Exercised	2.91
Weighted-average exercise price, Cancelled/Forfeited	8.42
Weighted-average exercise price, Outstanding, Balance	5.90	$ 5.89
Weighted-average exercise price, Options vested and exercisable	$ 4.94
Weighted-average remaining contractual life, options outstanding	7 years 7 months 28 days	7 years 9 months 26 days
Weighted-average remaining contractual life, options vested and exercisable	6 years 7 months 6 days