Note 12 - Equity Instruments (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Issued During Period, Shares, Employee Benefit Plan	94,684
Issuance of Stock to Defined Contribution Plan for Employer Matching Contribution	$ 35,980
Common Stock [Member]
Stock Issued During Period, Shares, Employee Benefit Plan	94,684
Employees [Member] \| Common Stock [Member]
Stock Issued During Period, Shares, Issued for Services	458,401	707,353
Stock Issued During Period, Value, Issued for Services	$ 165,000	$ 368,000
Director [Member] \| Common Stock [Member]
Stock Issued During Period, Shares, Issued for Services	0	16,406
Stock Issued During Period, Value, Issued for Services	$ 0	$ 10,500