Note 6 - Derivative Obligations (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Jun. 30, 2016
Class of Warrant or Right, Outstanding	14,300,208		14,300,208		4,828,723
Derivative, Gain (Loss) on Derivative, Net, Total	$ 308,000	$ 44,000	$ 567,000	$ 113,000
Series A Warrant [Member]
Class of Warrant or Right, Outstanding						404,412