Note 18 - Subsequent Events (Details Textual) - USD ($)			3 Months Ended	12 Months Ended		28 Months Ended	59 Months Ended
	Mar. 26, 2018	Feb. 06, 2018	Mar. 26, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 06, 2018	Dec. 31, 2017
Aggregate Offering Price, Additions				$ 13,500,000
Stock Issued During Period, Value, New Issues				$ 17,910,401	$ 6,775,016
ATM Agreement [Member]
Stock Issued During Period, Shares, New Issues				1,221,648			1,327,326
ATM Agreement [Member] | Subsequent Event [Member]
Aggregate Offering Price, Additions		$ 10,000,000				$ 17,500,000
Stock Issued During Period, Shares, New Issues			457,070
Stock Issued During Period, Value, New Issues			$ 1,300,000
Aggregate Offering Price, Remaining Amount	$ 12,200,000