Note 2 - Summary of Significant Accounting Policies - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Net loss	$ (282)	$ (2,501)	$ (4,189)	$ (1,538)	$ (1,589)	$ (2,150)	$ (6,972)	$ (5,277)
Less retained earning reduction related to round down feature triggered							(29)
Net loss, basic	(282)			(1,538)			(7,001)	(5,277)
Less gain on changes in fair value of warrant liability	(75)			(267)				(971)
Net loss, diluted	$ (357)			$ (1,805)			$ (7,001)	$ (6,248)
Weighted average shares outstanding, basic (in shares)	23,096			17,089			19,623	16,864
Net loss per share, basic (in dollars per share)	$ (0.01)			$ (0.09)			$ (0.36)	$ (0.31)
Effect of dilutive warrants (in shares)	117			59				192
Weighted average shares outstanding, diluted (in shares)	23,213			17,148			19,623	17,056
Net loss per share, diluted (in dollars per share)	$ (0.02)			$ (0.11)			$ (0.36)	$ (0.37)