Net Loss Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (22,033)	$ (22,033)	$ (6,289)	$ (54,592)	$ (87,823)
Denominator:
Weighted-average number of common shares used in loss per share - basic (in shares)	47,288,212		46,493,126	47,173,337	46,395,124
Weighted-average number of common shares used in loss per share - diluted (in shares)	47,288,212		46,493,126	47,173,337	46,395,124
Loss per share - basic (in dollars per share)	$ (0.47)		$ (0.14)	$ (1.16)	$ (1.89)
Loss per share - diluted (in dollars per share)	$ (0.47)		$ (0.14)	$ (1.16)	$ (1.89)