Note 4 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 3,869	$ 3,934	$ 8,919	$ 4,154
Denominator for basic earnings per share - weighted average shares outstanding	3,556,550	3,532,079	3,555,804	3,527,373
Effect of dilutive securities - employee stock options	693			1,018
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,557,243	3,532,079	3,555,804	3,528,391
Earnings per share - basic	$ 1.09	$ 1.11	$ 2.51	$ 1.18
Earnings per share - diluted	$ 1.09	$ 1.11	$ 2.51	$ 1.18