Net Loss Per Common Share -Schedules of Net Loss Per Share and Dilutive Securities (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic and diluted net loss per common share calculation:
Net loss	$ (30,143)	$ (26,795)	$ (18,589)	$ (15,076)	$ (56,938)	$ (33,665)
Weighted average common shares outstanding - basic (in shares)	93,409		57,421		93,382	55,424
Weighted average common shares outstanding - dilutive (in shares)	93,409		57,421		93,382	55,424
Net loss per share of common stock - basic (in dollars per share)	$ (0.32)		$ (0.32)		$ (0.61)	$ (0.61)
Net loss per share of common stock - diluted (in dollars per share)	$ (0.32)		$ (0.32)		$ (0.61)	$ (0.61)
Anti-dilutive securities
Total (in shares)	11,186		8,791		11,186	8,791
Stock options outstanding
Anti-dilutive securities
Total (in shares)	9,233		7,155		9,233	7,155
Restricted stock units
Anti-dilutive securities
Total (in shares)	1,953		1,636		1,953	1,636