Condensed Consolidated Statements of Stockholders' Equity (Deficit) - 9 months ended Sep. 30, 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	May 2018 Registered Direct Offering	May 2018 Registered Direct Offering Common Stock	May 2018 Registered Direct Offering Additional paid-in capital	July 2018 Registered Direct Offering	July 2018 Registered Direct Offering Common Stock	July 2018 Registered Direct Offering Additional paid-in capital
Beginning balance at Dec. 31, 2017	$ 9,007		$ 0	$ 5	$ 187,805	$ (178,803)
Balance, preferred stock (shares) at Dec. 31, 2017		8,000	8,000
Balance, common stock (shares) at Dec. 31, 2017	5,189,755			5,189,755
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of pre-funded warrants (shares)				483,221
Conversion of pre-funded warrants	$ 24			$ 1	23
Stock-based compensation expense	393				393
Registered Direct Offering, net of offering costs (in shares)								2,038,224			1,474,080
Registered Direct Offering, net of offering costs							$ 5,324	$ 2	$ 5,322	$ 3,591	$ 1	$ 3,590
Exercise of warrants (in shares)				129,702
Exercise of warrants	499				499
Net loss	(8,654)					(8,654)
Ending balance at Sep. 30, 2018	$ 10,184		$ 0	$ 9	$ 197,632	$ (187,457)
Balance, preferred stock (shares) at Sep. 30, 2018		8,000	8,000
Balance, common stock (shares) at Sep. 30, 2018	9,314,982			9,314,982