Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning Balance at Dec. 31, 2014	$ 51,922	$ 91	$ 447,510	$ (395,667)	$ (12)
Beginning Balance, shares at Dec. 31, 2014		9,033
Net loss	(9,238)			(9,238)
Other comprehensive income (loss)	52				52
Issuance of common stock	775	$ 1	774
Issuance of common stock, shares		86
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	(20)		(20)
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		35
Non-cash compensation expense related to grant of equity based compensation	1,902		1,902
Ending Balance at Dec. 31, 2015	45,393	$ 92	450,166	(404,905)	40
Ending Balance, shares at Dec. 31, 2015		9,154
Net loss	(8,973)			(8,973)
Other comprehensive income (loss)	(15)				(15)
Issuance of common stock	7,753	$ 18	7,735
Issuance of common stock, shares		1,841
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	(9)	$ 1	(10)
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		57
Non-cash compensation expense related to grant of equity based compensation	990		990
Ending Balance at Dec. 31, 2016	$ 45,139	$ 111	458,881	(413,878)	25
Ending Balance, shares at Dec. 31, 2016	11,052	11,052
Net loss	$ (12,960)			(12,960)
Other comprehensive income (loss)	97		(100)	100	97
Issuance of common stock	17,956	$ 107	17,849
Issuance of common stock, shares		10,704
Issuance of pre-funded warrants	12,588		12,588
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	1		1
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		46
Non-cash compensation expense related to grant of equity based compensation	756		756
Ending Balance at Dec. 31, 2017	$ 63,577	$ 218	$ 489,975	$ (426,738)	$ 122
Ending Balance, shares at Dec. 31, 2017	21,802	21,802