Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (40,459)	$ (45,364)	$ (161,938)	$ (121,175)
Other comprehensive loss, before tax:
Unrealized gain (loss) on available-for-sale investments	(2,697)	462	1,431	(668)
Foreign currency translation gain (loss)	(66)	10	(28)	12
Comprehensive loss, before tax	(43,222)	(44,892)	(160,535)	(121,831)
Income tax benefit (expense) related to items of other comprehensive loss	643		(341)
Comprehensive loss, net of tax	$ (42,579)	$ (44,892)	$ (160,876)	$ (121,831)