Share-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Options
Outstanding at beginning of period (in shares)	3,259	2,231
Granted (in shares)	1,212	1,168
Forfeited and Expired (in shares)	(264)	(140)
Exercised (in shares)	(61)	0
Outstanding at end of period (in shares)	4,146	3,259	2,231
Vested or expected to vest (in shares)	4,026
Exercisable at end of period (in shares)	1,855
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 8.14	$ 10.42
Granted (in dollars per share)	4.73	3.32
Forfeited and Expired (in dollars per share)	7.52	4.36
Exercised (in dollars per share)	1.58
Outstanding at end of period (in dollars per share)	7.28	$ 8.14	$ 10.42
Vested or expected to vest at end of period (in dollars per share)	7.36
Exercisable at end of period (in dollars per share)	$ 10.44
Weighted Average Remaining Contractual Term in Years
Weighted average remaining contractual term	7 years 10 months 17 days	8 years 5 months 1 day	8 years 11 months 8 days
Weighted average remaining contractual term, vested or expected to vest	7 years 10 months 6 days
Weighted average remaining contractual term, exercisable	6 years 11 months 23 days
Aggregate Intrinsic Value
Intrinsic value	$ 1,423	$ 2,978	$ 689
Intrinsic value, vested or expected to vest at end of period	1,377
Intrinsic value, exercisable at end of period	$ 365