CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss	$ (278,017)	$ (236,455)	$ (215,524)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments, net of tax	(98)	311	567
Comprehensive loss	$ (278,115)	$ (236,144)	$ (214,957)