Note 13 - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Outstanding-Number of options (in shares)	116,550	103,350	95,075
Exercised-Number of options (in shares)	(19,025)	(9,550)	(14,925)
Forfeited-Number of options (in shares)	(8,575)	(2,250)	(1,500)
Granted-Number of options (in shares)	25,000	25,000	24,700
Outstanding ending-Number of options (in shares)	113,950	116,550	103,350
Exercisable-Number of options (in shares)	43,125
Outstanding-Weighted average exercise price (in dollars per share)	$ 37.42	$ 36.96	$ 35.11
Exercised-Weighted average exercise price (in dollars per share)	30.97	29.39	27.16
Forfeited-Weighted average exercise price (in dollars per share)	35.27	39.86	37.20
Granted-Weighted average exercise price (in dollars per share)	32.50	36.50	38.15
Outstanding ending-Weighted average exercise price (in dollars per share)	37.58	$ 37.42	$ 36.96
Exercisable-Weighted average exercise price (in dollars per share)	$ 40.72
Outstanding ending-Weighted average remaining contractual term	2 years 2 months 12 days
Exercisable-Weighted average remaining contractual term	7 months 24 days
Outstanding ending-Aggregate intrinsic value	$ 84