Condensed Consolidated Statements of Stockholders' Equity (Deficit) (unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Preferred Stock Series A Convertible Preferred Stock	Common Stock	Additional paid-in capital	Accumulated deficit
Beginning balance at Dec. 31, 2017	$ 9,007		$ 0	$ 26	$ 187,784	$ (178,803)
Balance, preferred stock (shares) at Dec. 31, 2017		8,000	8,000
Balance, common stock (shares) at Dec. 31, 2017	25,940,247			25,940,247
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of pre-funded warrants	$ 24			$ 2	22
Conversion of pre-funded warrants (shares)				2,416,104
Stock-based compensation expense	129				129
Net loss	(2,901)					(2,901)
Ending balance at Mar. 31, 2018	$ 6,259		$ 0	$ 28	$ 187,935	$ (181,704)
Balance, preferred stock (shares) at Mar. 31, 2018		8,000	8,000
Balance, common stock (shares) at Mar. 31, 2018	28,356,351			28,356,351