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	$ (53,276)	$ (67,323)	$ (129,582)	$ (142,698)
Change in net unrealized gain on available-for-sale investments, net of tax	7,980	1,172	5,131	3,269
Comprehensive loss	$ (45,296)	$ (66,151)	$ (124,451)	$ (139,429)