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, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (1,752,857)	$ (2,602,241)	$ (911,335)
Weighted-average shares used in computing net loss per share, basic and diluted (in shares)	312,175,000	227,498,000	21,176,000
Net loss per share, basic and diluted (in dollars per share)	$ (5.61)	$ (11.44)	$ (43.04)