Stock-Based Compensation - Schedule of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019
NUMBER OF SHARES
Beginning balance (in shares)	6,935,119
Granted (in shares)	2,046,583
Exercised (in shares)	(139,119)
Canceled (in shares)	(307,317)
Ending balance (in shares)	8,535,266
Options exercisable (in shares)	5,404,516
WEIGHTED AVERAGE EXERCISE PRICE
Beginning balance (in dollars per share)	$ 28.96
Granted (in dollars per share)	32.54
Exercised (in dollars per share)	28.74
Canceled (in dollars per share)	51.53
Ending balance (in dollars per share)	29.02
Options exercisable (in dollars per share)	$ 23.00
WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE (YEARS)
Options outstanding, weighted average remaining contractual life	6 years 9 months 18 days
Options exercisable, weighted average remaining contractual life	5 years 4 months 24 days
AGGREGATE INTRINSIC VALUE
Options outstanding	$ 28,534
Options exercisable	$ 28,304