Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (125,519)	$ (80,000)	$ (248,486)	$ (218,651)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments	(64)	7,688	(830)	2,567
Net foreign currency translation gain (loss)	(215)	(96)	(275)	(847)
Other comprehensive income (loss)	(279)	7,592	(1,105)	1,720
Comprehensive loss	$ (125,798)	$ (72,408)	$ (249,591)	$ (216,931)