Note 7 - Derivative Obligations (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jun. 30, 2016
Class of Warrant or Right, Outstanding	16,681,788		17,265,208
Derivative, Gain (Loss) on Derivative, Net, Total	$ 0	$ 259,000
Series A Warrant [Member]
Class of Warrant or Right, Outstanding				404,412