Note 8 - Earnings Per Share - Calculation of Diluted Shares (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss) attributable to common stockholders	$ 1,151,094	$ (424,968)	$ 2,094,246	$ (2,063,470)
Weighted average shares outstanding used to compute basic earnings per share (in shares)	17,273,412	13,238,248	15,529,026	13,102,238
Effect of dilutive securities (in shares)	6,383,221		5,522,193
Weighted average diluted shares (in shares)	23,656,633	13,238,248	21,051,219	13,102,238
Basic net income (loss) per common share (in dollars per share)	$ 0.07	$ (0.03)	$ 0.13	$ (0.16)
Diluted net income (loss) per common share (in dollars per share)	$ 0.05	$ (0.03)	$ 0.10	$ (0.16)