Note 7 - Stock-based Compensation - Stock Option Activity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Stock Option Plan 2013 [Member]
Options outstanding, Shares (in shares)	165,517	189,917
Options outstanding, Weighted average exercise price (in dollars per share)	$ 21.52	$ 21.14
Options exercised, Shares (in shares)	(23,765)	(24,400)
Options exercised, Weighted average exercise price (in dollars per share)	$ 15.06	$ 18.59
Options outstanding, Shares (in shares)	141,752	165,517
Options outstanding, Weighted average exercise price (in dollars per share)	$ 22.6	$ 21.52
Options outstanding, Weighted average remaining contractual term in years (Year)	3 years
Options outstanding, Intrinsic value	$ 2,011,461
Options exercisable, Shares (in shares)	141,752
Options exercisable, Weighted average exercise price (in dollars per share)	$ 22.6
Options exercisable, weighted average remaining contractual term (Year)	3 years
Options exercisable, Intrinsic value	$ 2,011,461
Options granted, shares (in shares)		0
Stock Option Plan 2022 [Member]
Options outstanding, Shares (in shares)	105,500	117,200
Options outstanding, Weighted average exercise price (in dollars per share)	$ 31	$ 31
Options exercised, Shares (in shares)	(1,300)	(1,300)
Options exercised, Weighted average exercise price (in dollars per share)	$ 31	$ 31
Options outstanding, Shares (in shares)	211,400	105,500
Options outstanding, Weighted average exercise price (in dollars per share)	$ 32.56	$ 31
Options outstanding, Weighted average remaining contractual term in years (Year)	8 years 11 months 15 days
Options outstanding, Intrinsic value	$ 894,902
Options exercisable, Shares (in shares)	21,800
Options exercisable, Weighted average exercise price (in dollars per share)	$ 31
Options exercisable, weighted average remaining contractual term (Year)	7 years 11 months 4 days
Options exercisable, Intrinsic value	$ 126,222
Options cancelled, Shares (in shares)		(10,400)
Options cancelled, Weighted average exercise price (in dollars per share)		$ 31
Options granted, shares (in shares)	107,200
Options granted, Weighted average exercise price (in dollars per share)	$ 34.07
Expected to vest, Shares (in shares)	163,397
Expected to vest, Weighted average exercise price (in dollars per share)	$ 32.56
Expected to vest, Weighted average remaining contractual term in years (Year)	9 years 29 days
Expected to vest, Intrinsic value	$ 691,696