Net Income (Loss) Per Share - Computation of Basic and Diluted Net (Loss) Income Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income (loss)	$ 2,226	$ (14,483)	$ (11,596)	$ (30,737)	$ 13,224	$ (41,248)	$ (23,853)	$ (58,761)
Accretion of redeemable series A-1 preferred stock				(6,542)				(17,601)
Redeemable series A-1 preferred stock deemed dividend				(24,341)				(24,341)
Convertible and redeemable series A-2 preferred stock dividend	(4,100)			(2,870)			(12,300)	(2,870)
Net loss attributable to common stockholders –basic and diluted	$ (1,874)			$ (64,490)			$ (36,153)	$ (103,573)
Weighted-average common shares outstanding – basic and diluted	26,220			21,554			25,798	13,669
NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS— BASIC AND DILUTED	$ (0.07)			$ (2.99)			$ (1.40)	$ (7.58)