Note 8 - Stock-based Compensation Expense - Outstanding and Exercisable Options (Details)	6 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares
Exercise price range, lower limit (in dollars per share)	$ 13.01
Exercise price range, upper limit (in dollars per share)	$ 16.00
Number of options outstanding (in shares) | shares	244,000
Number of options outstanding, weighted average remaining contractual term (Year)	9 years 8 months 12 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 14.11
Number of options outstanding, intrinsic value | $	$ 0
Number of options exercisable (in shares) | shares	0
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 0
Number of options exercisable, intrinsic value | $	$ 0
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	511,125
Number of options outstanding, weighted average remaining contractual term (Year)	8 years 3 months 18 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 4.55
Number of options outstanding, intrinsic value | $	$ 1,443,308
Number of options exercisable (in shares) | shares	133,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 4.45
Number of options exercisable, intrinsic value | $	$ 388,093
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)	4 years 9 months 18 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)	$ 13.00
Number of options outstanding (in shares) | shares	130,000
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)	$ 11.51
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