NET LOSS PER SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (117,469)	$ (15,514)	$ (237,275)	$ (62,377)
Less: Premium on repurchase of redeemable convertible preferred stock	0	0	(13,407)	0
Net loss attributable to common stockholder, basic	(117,469)	(15,514)	(250,682)	(62,377)
Net loss attributable to common stockholder, diluted	$ (117,469)	$ (15,514)	$ (250,682)	$ (62,377)
Denominator:
Weighted average shares outstanding, basic and diluted (in shares)	377,660,477	260,534,724	318,315,891	260,449,607
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.31)	$ (0.06)	$ (0.79)	$ (0.24)