Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (86,142)	$ (38,502)	$ (191,839)	$ (121,441)
Other comprehensive loss, before tax:
Unrealized gain on available-for-sale investments	3,206	1,952	1,564	4,128
Foreign currency adjustment	0	0	25	0
Comprehensive loss, before tax	(82,936)	(36,550)	(190,250)	(117,313)
Income tax expense related to items of other comprehensive loss	0	(464)	0	(984)
Comprehensive loss, net of tax	$ (82,936)	$ (37,014)	$ (190,250)	$ (118,297)