CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net loss	$ (183,769)	$ (279,966)	$ (156,937)
Other comprehensive income (loss):
Net unrealized (losses) gains on marketable securities available-for-sale	(50)	54	42
Foreign currency translation adjustment	3,247	(2,744)	(2,561)
Other comprehensive income (loss)	3,197	(2,690)	(2,519)
Comprehensive loss	$ (180,572)	$ (282,656)	$ (159,456)