Note 5 - Share-based Compensation Plans - Stock Option Activity (Details) - The 2020 Equity Incentive Plan [Member]	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares
Outstanding, shares (in shares) | shares	839,400
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 2.20
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares) | shares	248,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 3.11
Exercised, shares (in shares) | shares	(109,700)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 1.78
Forfeited, shares (in shares) | shares	(15,400)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 2.88
Expired, shares (in shares) | shares	(900)
Expired, weighted average exercise price (in dollars per share) | $ / shares	$ 1.68
Outstanding, shares (in shares) | shares	961,400
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 2.47
Outstanding, weighted remaining contractual life (Year)	6 years 1 month 20 days
Outstanding, Aggregate intrinsic value | $	$ 2,375,619
Options exercisable, shares (in shares) | shares	498,300
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 2.08
Options exercisable, weighted remaining contractual life (Year)	4 years 2 months 4 days
Options exercisable, Aggregate intrinsic value | $	$ 1,064,670