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, 2022	Dec. 31, 2021	Dec. 31, 2020
Exercised, number of options (in shares)	23,581	116,753	630,373
Common Stock Options [Member]
Beginning balance, outstanding, number of options (in shares)	477,640
Beginning balance, outstanding, weighted average exercise price (in dollars per share)	$ 30.88
Granted, number of options (in shares)	127,227	101,091	70,471
Granted, weighted average exercise price (in dollars per share)	$ 36.67
Exercised, number of options (in shares)	23,581
Exercised, weighted average exercise price (in dollars per share)	$ 13.17
Ending balance, outstanding, number of options (in shares)	581,286	477,640
Ending balance, outstanding, weighted average exercise price (in dollars per share)	$ 32.86	$ 30.88
Outstanding, weighted average remaining contractual term (Year)	5 years 5 months 8 days
Outstanding, aggregate intrinsic value	$ 4,739
Exercisable, number of options (in shares)	323,140
Weighted average exercise price (in dollars per share)	$ 26.97
Exercisable, weighted average remaining contractual term (Year)	3 years 6 months 18 days
Exercisable, aggregate intrinsic value	$ 4,369