CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,182)	$ (50,211)
Other comprehensive income:
Unrealized losses on available for sale securities, net of tax of $0, $0, $0 and $0	43	(256)
Total comprehensive loss	$ (11,139)	$ (50,467)