Net Loss per Share Attributable to Common Stock - Computation of Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (27,878)	$ (6,611)	$ (63,662)	$ (66,728)
Dividends on convertible preferred stock	(1,878)	(1,284)	(4,214)	(1,284)
Net loss attributable to common stock - basic	(29,756)	(7,895)	(67,876)	(68,012)
Net loss attributable to common stock - diluted	$ (29,756)	$ (7,895)	$ (67,876)	$ (68,012)
Denominator:
Weighted average shares - basic (in shares)	104,391,337	98,785,318	103,912,212	96,114,012
Weighted averages shares - diluted (in shares)	104,391,337	98,785,318	103,912,212	96,114,012
Earnings Per Share, Basic and Diluted [Abstract]
Net loss per share attributable to common stock - basic (in dollars per share)	$ (0.29)	$ (0.08)	$ (0.65)	$ (0.71)
Net loss per share attributable to common stock - diluted (in dollars per share)	$ (0.29)	$ (0.08)	$ (0.65)	$ (0.71)