Note 4 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 3,778	$ 3,090	$ 7,932	$ 9,612
Denominator for basic earnings per share - weighted average shares outstanding	3,542,805	3,501,771	3,532,555	3,494,471
Effect of dilutive securities - employee stock options		6,546	122	7,036
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,542,805	3,508,317	3,532,677	3,501,507
Earnings per share - basic	$ 1.07	$ 0.88	$ 2.25	$ 2.75
Earnings per share - diluted	$ 1.07	$ 0.88	$ 2.25	$ 2.75