CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (209,383)	$ (419,503)	$ (123,914)
Other comprehensive income (loss):
Net unrealized (loss) gains on marketable securities	(183)	702	3
Reclassification adjustments for realization of gain on sale of marketable securities included in net loss	(7)	(326)	0
Foreign currency translation loss	(260)	0	0
Total other comprehensive (loss) income	(450)	376	3
Comprehensive loss	$ (209,833)	$ (419,127)	$ (123,911)