Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (523,837)	$ (444,440)	$ (440,667)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments	(1,568)	(927)	5,693
Net foreign currency translation gain (loss)	(294)	(363)	(382)
Other comprehensive income (loss)	(1,862)	(1,290)	5,311
Comprehensive loss	$ (525,699)	$ (445,730)	$ (435,356)