Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at Dec. 31, 2014	$ 41,196	$ 1,317	$ 249,032	$ (208,447)	$ (706)
Balance, shares at Dec. 31, 2014		131,743,365
Issuance of common stock	42,850	$ 230	42,620
Issuance of common stock, shares		23,000,000
Common stock issued under equity compensation plan, net of shares withheld for taxes	(49)	$ 1	(50)
Common stock issued under equity compensation plan, net of shares withheld for taxes, shares		85,147
Exercise of warrants and options	31		31
Exercise of warrants and options, shares		20,000
Share-based compensation	3,659		3,659
Net loss	(20,659)			(20,659)
Other comprehensive income (loss)	14				14
Balance at Dec. 31, 2015	67,042	$ 1,548	295,292	(229,106)	(692)
Balance, shares at Dec. 31, 2015		154,848,512
Common stock issued under equity compensation plan, net of shares withheld for taxes	(84)	$ 2	(86)
Common stock issued under equity compensation plan, net of shares withheld for taxes, shares		216,389
Exercise of options	101	$ 1	100
Exercise of options, shares		102,776
Share-based compensation	2,520		2,520
Net loss	(24,339)			(24,339)
Other comprehensive income (loss)	(23)				(23)
Balance at Dec. 31, 2016	45,218	$ 1,552	297,826	(253,445)	(715)
Balance, shares at Dec. 31, 2016		155,167,677
Common stock issued under equity compensation plan, net of shares withheld for taxes	(249)	$ 2	(251)
Common stock issued under equity compensation plan, net of shares withheld for taxes, shares		195,534
Exercise of options	1,816	$ 13	1,803
Exercise of options, shares		1,311,293
Share-based compensation	3,490		3,490
Net loss	(16,743)			(16,743)
Cumulative effect of change in accounting principle			97	(97)
Other comprehensive income (loss)	15				15
Balance at Dec. 31, 2017	$ 33,547	$ 1,567	$ 302,965	$ (270,285)	$ (700)
Balance, shares at Dec. 31, 2017		156,674,504