Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (42,854)	$ (67,982)
Other comprehensive loss:
Net unrealized loss on marketable securities	(43)	(11)
Total comprehensive loss	$ (42,897)	$ (67,993)