Note 2 - Basic and Diluted Earnings (Loss) Per Share - Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income (loss)	$ (238,305)	$ 523,793
Denominator for basic earnings (loss) per share – weighted average shares (in shares)	1,845,000	1,845,000
Dilutive effect of employee stock options and other warrants (in shares)		1,000
Denominator for diluted earnings (loss) per share – adjusted weighted average shares (in shares)	1,845,000	1,846,000
Basic earnings (loss) per share (in dollars per share)	$ (0.13)	$ 0.28
Diluted earnings (loss) per share (in dollars per share)	$ (0.13)	$ 0.28