Net Loss Per Share - Reconciliation of Shares Used in Calculating Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net loss (in thousands)	$ (32,807)	$ (21,119)	$ (21,195)	$ (38,710)	$ (18,627)	$ (37,001)	$ (75,121)	$ (94,338)
Weighted average number of shares outstanding, basic and diluted	69,798,839			66,451,414			68,926,203	65,504,571
Net loss per share, basic and diluted	$ (0.47)			$ (0.58)			$ (1.09)	$ (1.44)