Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)	5,023
Granted (in shares)	1,418
Exercised (in shares)	(185)	(683)
Cancelled or forfeited (in shares)	(521)
Ending outstanding balance (in shares)	5,735	5,023
Exercisable (in shares)	3,586
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning outstanding balance (in dollars per share)	$ 10.23
Granted (in dollars per share)	4.37
Exercised (in dollars per share)	2.36
Cancelled or forfeited (in dollars per share)	13.19
Ending outstanding balance (in dollars per share)	8.76	$ 10.23
Exercisable (in dollars per share)	$ 7.41
Remaining contractual life, outstanding	7 years 2 months 9 days	7 years 6 months 26 days
Remaining contractual life, exercisable	6 years 4 months 13 days
Aggregate intrinsic value, outstanding	$ 18,959	$ 3,133
Aggregate intrinsic value, exercisable	$ 13,864