Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (644,239)	$ (1,138,473)	$ (178,903)	$ (234,339)	$ (1,782,712)	$ (413,242)
Weighted-average shares used in computing net loss per share, basic and diluted	288,372		21,088		156,647	20,566
Net loss per share, basic and diluted	$ (2.23)		$ (8.48)		$ (11.38)	$ (20.09)