Net Loss per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
	Nov. 26, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss attributable to Class A and Class B common stockholders		$ (157,553)	$ (304,414)	$ (273,540)
Deemed dividend	$ (2,500)	0	(2,454)	0
Net loss available to Class A and Class B common stockholders		$ (157,553)	$ (306,868)	$ (273,540)
Denominator:
Weighted average shares used to compute net loss per share available to Class A and Class B common stockholders, basic and diluted (in shares)		138,722	115,118	53,268
Net loss per share attributable to Class A and Class B common stockholders, basic and diluted (in dollars per share)		$ (1.14)	$ (2.67)	$ (5.14)