Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (42,264)	$ (42,794)	$ (101,481)	$ (87,109)
Other comprehensive income (loss)
Change in unrealized losses on marketable securities, net of tax	(46)	0	(46)	0
Comprehensive loss	$ (42,310)	$ (42,794)	$ (101,527)	$ (87,109)