Note 8 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Outstanding at beginning of year, options (in shares)	384,500	434,500
Outstanding at beginning of year, option, weighted average exercise price (in dollars per share)	$ 2.98	$ 3.05
Granted, options (in shares)	0	0
Granted, option, weighted average exercise price (in dollars per share)	$ 0	$ 0
Exercised, options (in shares)	(44,000)	0
Exercised, option, weighted average exercise price (in dollars per share)	$ 0.96	$ 0
Expired or forfeited, options (in shares)	(70,000)	(50,000)
Expired or forfeited, option, weighted average exercise price (in dollars per share)	$ 3.85	$ 3.55
Outstanding at end of year, options (in shares)	270,500	384,500
Outstanding at end of year, option, weighted average exercise price (in dollars per share)	$ 3.09	$ 2.98
Exercisable, options (in shares)	270,500	384,500
Exercisable, option, weighted average exercise price (in dollars per share)	$ 3.09	$ 2.98
Weighted-Average Remaining Contractual Life (years) (Year)	1 year 6 months 21 days	2 years 5 months 4 days
Aggregate Intrinsic Value	$ 4	$ 27