Note 9 - Share-based Compensation - Stock Option Activity Under Equity Incentive Plans and Director Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Exercised, number of options (in shares)	87,378	23,581	116,753
Common Stock Options [Member]
Beginning balance, outstanding, number of options (in shares)	581,286
Beginning balance, outstanding, weighted average exercise price (in dollars per share)	$ 32.86
Granted, number of options (in shares)	96,359	127,227	101,091
Granted, weighted average exercise price (in dollars per share)	$ 40.55
Exercised, number of options (in shares)	87,378
Exercised, weighted average exercise price (in dollars per share)	$ 20.89
Forfeited, number of options (in shares)	21,099
Forfeited, weighted average exercise price (in dollars per share)	$ 40.52
Ending balance, outstanding, number of options (in shares)	569,168	581,286
Ending balance, outstanding, weighted average exercise price (in dollars per share)	$ 35.72	$ 32.86
Outstanding, weighted average remaining contractual term (Year)	5 years 9 months
Outstanding, aggregate intrinsic value	$ 3,971
Exercisable, number of options (in shares)	346,032
Weighted average exercise price (in dollars per share)	$ 30.73
Exercisable, weighted average remaining contractual term (Year)	4 years 6 months 18 days
Exercisable, aggregate intrinsic value	$ 3,894