CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Statement - 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	$ (24,896)	$ (29,097)	$ (31,066)	$ (51,194)
Share of other comprehensive income (loss) of equity method investments	0	5	0	3
Reclassification adjustment for sale of equity method investments	(1)	0	81	50
Total comprehensive loss	$ (24,897)	$ (29,092)	$ (30,985)	$ (51,141)