Note 4 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 3,379	$ 2,935
Denominator for basic earnings per share - weighted average shares outstanding	3,486,786	3,452,531
Effect of dilutive securities - employee stock options	7,643	20,374
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,494,429	3,472,905
Earnings per share - basic	$ 0.97	$ 0.85
Earnings per share - diluted	$ 0.97	$ 0.85