Condensed Consolidated Statements Of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (28,256)	$ (39,057)	$ (61,273)	$ (50,086)
Other comprehensive income (loss):
Net unrealized gains (losses) on available-for-sale securities, net of tax	64	16	(153)	54
Other comprehensive income (loss)	64	16	(153)	54
Comprehensive loss	$ (28,192)	$ (39,041)	$ (61,426)	$ (50,032)