Note 6 - Shareholders' Equity - Summary of Certain Additional Information about Stock Options (Details) - Share-Based Payment Arrangement, Option [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Weighted average grant-date fair value of options granted during the period (in dollars per share)	$ 1.40	$ 2.75	$ 1.66	$ 2.88
Options in-the-money (in shares) (in shares)	222,373	629,272	222,373	629,272
Aggregate intrinsic value of options exercised during the period	$ 1.02	$ 1.20	$ 1.16	$ 1.88