Net Loss per 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
Numerator:
Net loss	$ (35,308)	$ (73,643)	$ (167,392)	$ (219,583)
Denominator:
Weighted-average ordinary shares outstanding	73,574	63,717	68,021	62,361
Less: weighted-average ordinary shares subject to forfeiture		(414)	(76)	(480)
Weighted-average ordinary shares used to compute basic net loss per share	73,574	63,303	67,945	61,881
Weighted-average ordinary shares used to compute diluted net loss per share	73,574	63,303	67,945	61,881
Basic net loss per share	$ (0.48)	$ (1.16)	$ (2.46)	$ (3.55)
Diluted net loss per share	$ (0.48)	$ (1.16)	$ (2.46)	$ (3.55)