Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (112,444)	$ (106,794)	$ (90,722)
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities available-for-sale	(8)	11	32
Cumulative foreign currency translation adjustments	(686)	(1,272)	(1,553)
Total other comprehensive loss	(694)	(1,261)	(1,521)
Total comprehensive loss	$ (113,138)	$ (108,055)	$ (92,243)