Note 6 - Warrants (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Class of Warrant or Right, Outstanding	4,075,005	4,080,005
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 4.35	$ 4.35
Class of Warrant or Right, Exercised During Period	5,000
Class of Warrant or Right, Exercised During Period, Exercise Price	$ 4.75
Proceeds from Warrant Exercises	$ 24,000