Stock-based Compensation - Service-based stock options (Details) - Service Based Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Service-based stock options activity
Shares outstanding, beginning (in shares)	6,182,873
Granted (in shares)	2,088,673
Exercised (in shares)	(254,335)
Expired (in shares)	0
Forfeited (in shares)	(617,994)
Shares outstanding, ending (in shares)	7,399,217	6,182,873
Exercisable at end of period (in shares)	4,287,676
Vested and expected to vest at end of period(in shares)	7,399,217
Service-based stock options weighted average exercise price
Beginning balance, Weighted average exercise price (in dollars per share)	$ 10.60
Granted, Weighted average exercise price (in dollars per share)	7.72
Exercised, Weighted average exercise price (in dollars per share)	4.09
Expired, Weighted average exercise price (in dollars per share)	0
Forfeited, Weighted average exercise price (in dollars per share)	12.96
Ending balance, Weighted average exercise price (in dollars per share)	9.81	$ 10.60
Options exercisable, Weighted average exercise price per share (in dollars per share)	9.43
Vested and expected to vest, Weighted average exercise price per share (in dollars per share)	$ 9.81
Service-based stock options, additional disclosures
Options outstanding, Weighted average remaining contractual life	6 years 4 months 13 days	6 years 8 months 1 day
Options exercisable, Weighted average remaining contractual life	4 years 8 months 4 days
Vested and expected to vest, Weighted average remaining contractual life	6 years 4 months 13 days