Note 8 - Basic and Diluted Earnings Per Common Share - Reconciliation of Net Income and Number of Shares Used in Computations of Basic and Diluted EPS (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Net income	$ 693,000	$ 1,522,000	$ 1,671,000	$ 3,719,000	$ 2,215,000	$ 5,390,000
Shares (denominator):
Basic weighted average common shares outstanding (in shares)	12,834,332		13,246,676		12,945,981	13,294,571
Add: dilutive effect of common stock options (in shares)	73,891		264,821		86,332	326,530
Diluted weighted average common shares outstanding (in shares)	12,908,223		13,511,497		13,032,313	13,621,101
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ 0.05		$ 0.13		$ 0.17	$ 0.41
Diluted earnings per common share (in dollars per share)	$ 0.05		$ 0.12		$ 0.17	$ 0.40