Note 4 - Stock-based Compensation - Stock Options Outstanding and Exercisable (Details)	6 Months Ended
	Jun. 30, 2023 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
Outstanding Weighted Average Contractual Life Remaining (Year)	5 years 1 month 6 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 17.35
Outstanding Aggregate Intrinsic Value | $	$ 582,520
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) | shares	13,000
Outstanding Weighted Average Contractual Life Remaining (Year)	3 years 8 months 12 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 3.75
Outstanding Aggregate Intrinsic Value | $	$ 280,940
Options Outstanding Exercise Price Range2 [Member]
Number Outstanding (in shares) | shares	8,000
Outstanding Weighted Average Contractual Life Remaining (Year)	4 years 10 months 24 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 7.80
Outstanding Aggregate Intrinsic Value | $	$ 140,480
Options Outstanding Exercise Price Range 3 [Member]
Number Outstanding (in shares) | shares	30,000
Outstanding Weighted Average Contractual Life Remaining (Year)	5 years 7 months 6 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 19.99
Outstanding Aggregate Intrinsic Value | $	$ 161,100
Options Outstanding Exercise Price Range 4 [Member]
Number Outstanding (in shares) | shares	8,000
Outstanding Weighted Average Contractual Life Remaining (Year)	5 years 10 months 24 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 39.11