Consolidated Statements of Stockholders' Deficit (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Common Warrant	Common Warrant Common Stock	Common Warrant Additional Paid-In Capital	Public Offering Pre Funded Warrant	Public Offering Pre Funded Warrant Common Stock	Public Offering Pre Funded Warrant Additional Paid-In Capital	Common Stock Purchase Agreement	Common Stock Purchase Agreement Common Stock	Common Stock Purchase Agreement Additional Paid-In Capital	Registered Direct Offering Pre Funded Warrant	Registered Direct Offering Pre Funded Warrant Common Stock	Registered Direct Offering Pre Funded Warrant Additional Paid-In Capital
Beginning balance, in shares (in shares) at Dec. 31, 2018		26,056,735
Beginning balance at Dec. 31, 2018	$ 6,438	$ 3	$ 195,483	$ (155)	$ (188,893)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	168		168
Exercise of stock options (in shares)		12,999
Exercise of stock options	10	$ 0	10
Net loss	(6,637)				(6,637)
Ending balance, in shares (in shares) at Mar. 31, 2019		26,069,734
Ending balance at Mar. 31, 2019	$ (735)	$ 3	195,661	(155)	(196,244)
Beginning balance, in shares (in shares) at Dec. 31, 2019	26,734,800	26,734,800
Beginning balance at Dec. 31, 2019	$ (22,283)	$ 3	197,853	(155)	(219,984)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	$ 385		385
Common stock issued during period (in shares)										15,498,602			700,000			10,550,000
Common stock issued during period									$ 5,158	$ 2	$ 5,156	$ 442	$ 0	$ 442	$ 7,225	$ 1	$ 7,224
Exercise of warrants (in shares)							9,600,000			4,333,334						4,602,326
Exercise of warrants						$ 2,880	$ 1	$ 2,879	$ 0	$ 0	$ 0				$ 0	$ 0	$ 0
Exercise of stock options (in shares)	0
Net loss	$ (6,167)				(6,167)
Ending balance, in shares (in shares) at Mar. 31, 2020	72,019,062	72,019,062
Ending balance at Mar. 31, 2020	$ (12,360)	$ 7	$ 213,939	$ (155)	$ (226,151)