Net Loss per Share Attributable to Common Stock - Computation of Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (18,527)	$ (80,805)	$ (41,978)
Net loss attributable to common stock—basic	$ (22,981)	$ (80,805)	$ (41,978)
Denominator:
Weighted average shares —basic and diluted (in shares)	98,574,529	91,583,533	85,669,039
Net loss per share attributable to common stock—basic and diluted (in dollars per share)	$ (0.23)	$ (0.88)	$ (0.49)
Net Income (Loss) Available to Common Stockholders, Diluted	$ (22,981)	$ (80,805)	$ (41,978)