Note 10 - Stock-based Compensation Plans - Stock Options Outstanding and Exercisable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Lower Range of Exercise Price (in dollars per share)	$ 3.50
Upper Range of Exercise Price (in dollars per share)	$ 39.11
Number Outstanding (in shares)	59,000	59,000	126,500
Outstanding Weighted Average Contractual Life Remaining (Year)	5 years 7 months 6 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 17.35
Outstanding Aggregate Intrinsic Value	$ 766,630
Options Outstanding Exercise Price Range1 [Member]
Lower Range of Exercise Price (in dollars per share)	$ 3.50
Upper Range of Exercise Price (in dollars per share)	$ 3.86
Number Outstanding (in shares)	13,000
Outstanding Weighted Average Contractual Life Remaining (Year)	4 years 2 months 12 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 3.75
Outstanding Aggregate Intrinsic Value	$ 371,680
Options Outstanding Exercise Price Range2 [Member]
Number Outstanding (in shares)	8,000
Outstanding Weighted Average Contractual Life Remaining (Year)	5 years 4 months 24 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 7.80
Outstanding Aggregate Intrinsic Value	$ 125,550
Options Outstanding Exercise Price Range 3 [Member]
Number Outstanding (in shares)	30,000
Outstanding Weighted Average Contractual Life Remaining (Year)	6 years 1 month 6 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 19.99
Outstanding Aggregate Intrinsic Value	$ 269,400
Options Outstanding Exercise Price Range 4 [Member]
Number Outstanding (in shares)	8,000
Outstanding Weighted Average Contractual Life Remaining (Year)	6 years 4 months 24 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 39.11
Outstanding Aggregate Intrinsic Value	$ 0