Net Loss per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net loss	$ (50,255)	$ (42,130)	$ (147,644)	$ (94,606)
Weighted-average common shares outstanding used in computation of basic loss per share	128,443	122,357	128,084	115,738
Basic loss per share (expressed in $ per share)	$ (0.39)	$ (0.34)	$ (1.15)	$ (0.82)
Weighted-average common shares outstanding used in computation of diluted loss per share	128,443	122,357	128,084	115,738
Diluted loss per share (expressed in $ per share)	$ (0.39)	$ (0.34)	$ (1.15)	$ (0.82)