Net Loss per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss from continuing operations	$ (29,824)	$ (27,536)	$ (71,731)	$ (64,091)
Net income (loss) from discontinued operations	60	(1,972)	4,599	(64,769)
Net loss	$ (29,764)	$ (29,508)	$ (67,132)	$ (128,860)
Denominator:
Weighted average shares outstanding, basic (in shares)	199,179,963	165,527,024	197,254,438	163,318,375
Weighted average shares outstanding, diluted (in shares)	199,179,963	165,527,024	197,254,438	163,318,375
Net Loss Per Share [Abstract]
Net loss from continuing operations per share, basic (in dollars per share)	$ (0.15)	$ (0.17)	$ (0.36)	$ (0.39)
Net loss from continuing operating per share, diluted (in dollars per share)	(0.15)	(0.17)	(0.36)	(0.39)
Net income (loss) from discontinued operations per share, basic (in dollars per share)	0	(0.01)	0.02	(0.40)
Net income (loss) from discontinued operations per share, diluted (in dollars per share)	0	(0.01)	0.02	(0.40)
Net loss per share, basic (in dollars per share)	(0.15)	(0.18)	(0.34)	(0.79)
Net loss per share, diluted (in dollars per share)	$ (0.15)	$ (0.18)	$ (0.34)	$ (0.79)