Note 2 - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2021		Sep. 30, 2021		Jun. 30, 2021		Mar. 31, 2021		Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Numerator for basic and diluted earnings per share - net income	$ 4,149		$ 3,424		$ 3,869		$ 5,050		$ 4,151		$ 3,778		$ 3,934		$ 220		$ 16,492	$ 12,083	$ 12,357
Denominator for basic earnings per share - weighted average shares outstanding																	3,553,949	3,537,323	3,498,326
Effect of dilutive securities - employee stock options																	189	37	5,824
Denominator for diluted earnings per share - adjusted weighted average shares outstanding																	3,554,138	3,537,360	3,504,150
Earnings per share - basic	$ 1.17	[1]	$ 0.96	[1]	$ 1.09	[1]	$ 1.42	[1]	$ 1.17	[1]	$ 1.07	[1]	$ 1.11	[1]	$ 0.06	[1]	$ 4.64	$ 3.42	$ 3.53
Earnings per share - diluted	$ 1.17	[1]	$ 0.96	[1]	$ 1.09	[1]	$ 1.42	[1]	$ 1.17	[1]	$ 1.07	[1]	$ 1.11	[1]	$ 0.06	[1]	$ 4.64	$ 3.42	$ 3.53

[1] Due to rounding, quarterly earnings per share may not sum to annual earnings per share