Note 10 - Subsequent Event (Details Textual)		3 Months Ended	12 Months Ended
	Apr. 08, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Common Stock, Shares Authorized		25,000,000	25,000,000
Common Stock, Shares, Outstanding, Ending Balance		18,302,880	18,228,887
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio		4
Subsequent Event [Member]
Common Stock, Shares Authorized	25,000,000
Common Stock, Shares, Outstanding, Ending Balance	18,269,546
Subsequent Event [Member] | Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	4
Before Reverse Stock Split [Member]
Common Stock, Shares Authorized		100,000,000
Common Stock, Shares, Outstanding, Ending Balance		73,211,520