Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,851)	$ (62,879)
Other comprehensive income (loss):
Unrealized gain on investments, net of taxes	10	5
Unrealized gain (loss) on currency translation	17	(2)
Other comprehensive income	27	3
Comprehensive loss	$ (17,824)	$ (62,876)