Note 7 - Stock-based Compensation - Stock Option Activity (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 $ / shares shares
Stock Option Plan 2013 [Member]
Options outstanding, Shares (in shares)	165,517	189,917
Options outstanding, Weighted average exercise price (in dollars per share) | $ / shares	$ 21.52	$ 21.14
Options exercised, Shares (in shares)	(24,070)	(24,400)
Options exercised, Weighted average exercise price (in dollars per share) | $ / shares	$ 15.18	$ 18.59
Options outstanding, Shares (in shares)	141,447	165,517
Options outstanding, Weighted average exercise price (in dollars per share) | $ / shares	$ 22.6	$ 21.52
Options outstanding, Weighted average remaining contractual term in years (Year)	2 years 9 months 18 days
Options outstanding, Intrinsic value | $	$ 1,892,476
Options exercisable, Shares (in shares)	141,447
Options exercisable, Weighted average exercise price (in dollars per share) | $ / shares	$ 22.6
Options exercisable, weighted average remaining contractual term (Year)	2 years 9 months 18 days
Options exercisable, Intrinsic value | $	$ 1,892,476
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) | $ / shares	$ 31	$ 31
Options exercised, Shares (in shares)	(1,300)	(1,300)
Options exercised, Weighted average exercise price (in dollars per share) | $ / shares	$ 31	$ 31
Options outstanding, Shares (in shares)	210,200	105,500
Options outstanding, Weighted average exercise price (in dollars per share) | $ / shares	$ 32.55	$ 31
Options outstanding, Weighted average remaining contractual term in years (Year)	8 years 8 months 15 days
Options outstanding, Intrinsic value | $	$ 721,385
Options exercisable, Shares (in shares)	21,800
Options exercisable, Weighted average exercise price (in dollars per share) | $ / shares	$ 31
Options exercisable, weighted average remaining contractual term (Year)	7 years 8 months 8 days
Options exercisable, Intrinsic value | $	$ 108,564
Options cancelled, Shares (in shares)	(1,200)	(10,400)
Options cancelled, Weighted average exercise price (in dollars per share) | $ / shares	$ 34.07	$ 31
Options granted, shares (in shares)	107,200
Options granted, Weighted average exercise price (in dollars per share) | $ / shares	$ 34.07
Expected to vest, Shares (in shares)	162,363
Expected to vest, Weighted average exercise price (in dollars per share) | $ / shares	$ 32.73
Expected to vest, Weighted average remaining contractual term in years (Year)	8 years 9 months 29 days
Expected to vest, Intrinsic value | $	$ 527,680