Net Loss per Share - Schedule of Computation of Net Loss per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (39,118)	$ (65,495)	$ (168,700)	$ (208,193)
Denominator:
Weighted average shares used in computing net loss per share, basic and diluted (shares)	224,807	212,207	221,329	204,855
Net loss per share—basic and diluted (in usd per share)	$ (0.17)	$ (0.31)	$ (0.76)	$ (1.02)