Condensed Consolidated Statement of Stockholders' Equity (Deficit) - 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
Balance, preferred stock (shares) at Dec. 31, 2017			8,000
Beginning balance at Dec. 31, 2017	$ 9,007		$ 0	$ 26	$ 187,784	$ (178,803)
Balance, common stock (shares) at Dec. 31, 2017				5,189,755
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of the May 2018 reverse stock split on common stock and additional paid in capital, beginning balance				$ (20)	20
Stock-based compensation expense	129				129
Conversion of pre-funded warrants (shares)				483,221
Conversion of pre-funded warrants	24				24
Net income (loss)	(2,901)					(2,901)
Balance, preferred stock (shares) at Mar. 31, 2018			8,000
Ending balance at Mar. 31, 2018	6,259		$ 0	$ 6	187,957	(181,704)
Balance, common stock (shares) at Mar. 31, 2018				5,672,976
Balance, preferred stock (shares) at Dec. 31, 2017			8,000
Beginning balance at Dec. 31, 2017	9,007		$ 0	$ 26	187,784	(178,803)
Balance, common stock (shares) at Dec. 31, 2017				5,189,755
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,795)
Balance, preferred stock (shares) at Jun. 30, 2018			8,000
Ending balance at Jun. 30, 2018	9,368		$ 0	$ 8	193,958	(184,598)
Balance, common stock (shares) at Jun. 30, 2018				7,840,902
Balance, preferred stock (shares) at Mar. 31, 2018			8,000
Beginning balance at Mar. 31, 2018	6,259		$ 0	$ 6	187,957	(181,704)
Balance, common stock (shares) at Mar. 31, 2018				5,672,976
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	131				131
Stock Issued During Period, Shares, New Issues								2,038,224
Stock Issued During Period, Value, New Issues							$ 5,373	$ 2	$ 5,371
Exercise of warrants (shares)				129,702
Exercise of warrants	499				499
Net income (loss)	(2,894)					(2,894)
Balance, preferred stock (shares) at Jun. 30, 2018			8,000
Ending balance at Jun. 30, 2018	9,368		$ 0	$ 8	193,958	(184,598)
Balance, common stock (shares) at Jun. 30, 2018				7,840,902
Balance, preferred stock (shares) at Dec. 31, 2018		8,000	8,000
Beginning balance at Dec. 31, 2018	$ 9,557		$ 0	$ 10	198,627	(189,080)
Balance, common stock (shares) at Dec. 31, 2018	9,758,332			9,758,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	$ 112				112
Net income (loss)	(3,666)					(3,666)
Balance, preferred stock (shares) at Mar. 31, 2019			8,000
Ending balance at Mar. 31, 2019	6,003		$ 0	$ 10	198,739	(192,746)
Balance, common stock (shares) at Mar. 31, 2019				9,758,332
Balance, preferred stock (shares) at Dec. 31, 2018		8,000	8,000
Beginning balance at Dec. 31, 2018	$ 9,557		$ 0	$ 10	198,627	(189,080)
Balance, common stock (shares) at Dec. 31, 2018	9,758,332			9,758,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 8,077
Balance, preferred stock (shares) at Jun. 30, 2019		8,000	8,000
Ending balance at Jun. 30, 2019	$ 17,863		$ 0	$ 10	198,856	(181,003)
Balance, common stock (shares) at Jun. 30, 2019	9,758,332			9,758,332
Balance, preferred stock (shares) at Mar. 31, 2019			8,000
Beginning balance at Mar. 31, 2019	$ 6,003		$ 0	$ 10	198,739	(192,746)
Balance, common stock (shares) at Mar. 31, 2019				9,758,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	117				117
Net income (loss)	11,743					11,743
Balance, preferred stock (shares) at Jun. 30, 2019		8,000	8,000
Ending balance at Jun. 30, 2019	$ 17,863		$ 0	$ 10	$ 198,856	$ (181,003)
Balance, common stock (shares) at Jun. 30, 2019	9,758,332			9,758,332