Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss		$ (22,996)	$ (8,558)	$ (7,581)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities, net of tax	[1]	(472)	(405)	547
Other comprehensive income (loss)		(472)	(405)	547
Total comprehensive loss		$ (23,468)	$ (8,963)	$ (7,034)

[1] Net of benefit from income taxes of $0, $0, and $314 in 2017, 2016 and 2015, respectively.