Note 6 - Stock Compensation Plans - Stock Options Outstanding and Exercisable (Details)	3 Months Ended
	Mar. 31, 2022 USD ($) $ / shares shares
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) | shares	59,000
Wgt. Avg. Contractual Life Remaining (yrs) (Year)	6 years 4 months 24 days
Wgt. Avg. Exercise Price (in dollars per share)	$ 17.35
Aggregate Intrinsic Value | $	$ 686,560
Exercisable Options (in shares) | shares	59,000
Weighted-Average Contractual Life Remaining - Exercisable (Year)	6 years 4 months 24 days
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 17.35
Aggregate Intrinsic Value - Exercisable | $	$ 686,560
Options Exercisable Exercise Price Range 1 [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) | shares	13,000
Wgt. Avg. Contractual Life Remaining (yrs) (Year)	5 years
Wgt. Avg. Exercise Price (in dollars per share)	$ 3.75
Aggregate Intrinsic Value | $	$ 346,560
Exercisable Options (in shares) | shares	13,000
Weighted-Average Contractual Life Remaining - Exercisable (Year)	5 years
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 3.75
Aggregate Intrinsic Value - Exercisable | $	$ 346,560
Options Outstanding Exercise Price Range2 [Member]
Lower Range of Exercise Price (in dollars per share)	$ 7.80
Number Outstanding (in shares) | shares	8,000
Wgt. Avg. Contractual Life Remaining (yrs) (Year)	6 years 2 months 12 days
Wgt. Avg. Exercise Price (in dollars per share)	$ 7.80
Aggregate Intrinsic Value | $	$ 117,700
Exercisable Options (in shares) | shares	8,000
Weighted-Average Contractual Life Remaining - Exercisable (Year)	6 years 2 months 12 days
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 7.80
Aggregate Intrinsic Value - Exercisable | $	$ 117,700
Options Outstanding Exercise Price Range 3 [Member]
Lower Range of Exercise Price (in dollars per share)	$ 19.99
Number Outstanding (in shares) | shares	30,000
Wgt. Avg. Contractual Life Remaining (yrs) (Year)	6 years 9 months 18 days
Wgt. Avg. Exercise Price (in dollars per share)	$ 19.99
Aggregate Intrinsic Value | $	$ 222,300
Exercisable Options (in shares) | shares	30,000
Weighted-Average Contractual Life Remaining - Exercisable (Year)	6 years 9 months 18 days
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 19.99
Aggregate Intrinsic Value - Exercisable | $	$ 222,300
Options Outstanding Exercise Price Range 4 [Member]
Lower Range of Exercise Price (in dollars per share)	$ 39.11
Number Outstanding (in shares) | shares	8,000
Wgt. Avg. Contractual Life Remaining (yrs) (Year)	7 years 2 months 12 days
Wgt. Avg. Exercise Price (in dollars per share)	$ 39.11
Exercisable Options (in shares) | shares	8,000
Weighted-Average Contractual Life Remaining - Exercisable (Year)	7 years 2 months 12 days
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 39.11