Note 4 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 220	$ 3,379
Denominator for basic earnings per share - weighted average shares outstanding	3,522,667	3,486,786
Effect of dilutive securities - employee stock options	2,788	7,643
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,525,455	3,494,429
Earnings per share - basic	$ 0.06	$ 0.97
Earnings per share - diluted	$ 0.06	$ 0.97