Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (2,602,241)	$ (911,335)	$ (688,301)
Weighted-average shares used in computing net loss per share, basic and diluted (in shares)	227,498,000	21,176,000	19,371,000
Net loss per share, basic and diluted (in dollars per share)	$ (11.44)	$ (43.04)	$ (35.53)