Note 4 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 3,710	$ 5,050
Denominator for basic earnings per share - weighted average shares outstanding	3,552,854	3,555,028
Effect of dilutive securities - employee stock options	1,602
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,554,456	3,555,028
Earnings per share - basic	$ 1.04	$ 1.42
Earnings per share - diluted	$ 1.04	$ 1.42