Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)	5,735
Granted (in shares)	957
Exercises of common stock options (in shares)	(9)	(24)
Cancelled or forfeited (in shares)	(40)
Ending outstanding balance (in shares)	6,643		5,735
Exercisable (in shares)	3,845
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)	$ 8.76
Granted (in dollars per share)	6.66
Exercised (in dollars per share)	4.21
Cancelled or forfeited (in dollars per share)	9.18
Ending outstanding balance (in dollars per share)	8.46		$ 8.76
Exercisable (in dollars per share)	$ 7.69
Remaining contractual life, outstanding	7 years 3 months 29 days		7 years 2 months 9 days
Remaining contractual life, exercisable	6 years 2 months 16 days
Aggregate intrinsic value, outstanding	$ 5,855		$ 18,959
Aggregate intrinsic value, exercisable	$ 5,264