Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (108,586)	$ (98,585)	$ (327,237)	$ (328,503)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments	(2,144)	(261)	423	6,621
Net foreign currency translation gain (loss)	349	(360)	(498)	(217)
Other comprehensive income (loss)	(1,795)	(621)	(75)	6,404
Comprehensive loss	$ (110,381)	$ (99,206)	$ (327,312)	$ (322,099)