Note 9 - Stock-based Compensation Expense - Outstanding and Exercisable Options (Details)	9 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares
Exercise Price Range 1 [Member]
Exercise price range, lower limit (in dollars per share)	$ 4.00
Exercise price range, upper limit (in dollars per share)	$ 7.00
Number of options outstanding (in shares) | shares	513,000
Number of options outstanding, weighted average remaining contractual term (Year)	8 years 9 months 18 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 4.51
Number of options outstanding, intrinsic value | $	$ 249,645
Number of options exercisable (in shares) | shares	125,500
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 4.94
Number of options exercisable, intrinsic value | $	$ 67,905
Exercise Price Range 2 [Member]
Exercise price range, lower limit (in dollars per share)	$ 7.01
Exercise price range, upper limit (in dollars per share)	$ 10.00
Number of options outstanding (in shares) | shares	20,000
Number of options outstanding, weighted average remaining contractual term (Year)	5 years 7 months 6 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 8.07
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	20,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 8.07
Number of options exercisable, intrinsic value | $	$ 0
Exercise Price Range 3 [Member]
Exercise price range, lower limit (in dollars per share)	$ 10.01
Exercise price range, upper limit (in dollars per share)	$ 12.00
Number of options outstanding (in shares) | shares	120,000
Number of options outstanding, weighted average remaining contractual term (Year)	4 years 6 months
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 10.52
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	120,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 10.52
Number of options exercisable, intrinsic value | $	$ 0
Exercise Price Range 4 [Member]
Exercise price range, lower limit (in dollars per share)	$ 12.01
Exercise price range, upper limit (in dollars per share)	$ 15.00
Number of options outstanding (in shares) | shares	25,000
Number of options outstanding, weighted average remaining contractual term (Year)	1 month 6 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 15.00
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	25,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 15.00
Number of options exercisable, intrinsic value | $	$ 0