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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 3,090	$ 3,211	$ 9,612	$ 9,008
Denominator for basic earnings per share - weighted average shares outstanding	3,501,771	3,466,672	3,494,471	3,459,906
Effect of dilutive securities - employee stock options	6,546	22,389	7,036	21,083
Denominator for diluted earnings per share - adjusted weighted average shares outstanding	3,508,317	3,489,061	3,501,507	3,480,989
Earnings per share - basic	$ 0.88	$ 0.93	$ 2.75	$ 2.60
Earnings per share - diluted	$ 0.88	$ 0.92	$ 2.75	$ 2.59