Note 13 - Outstanding Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	121,550	109,150	113,950	116,550
Exercise price, outstanding	$ 34.29	$ 37.65	$ 37.58	$ 37.42
Remaining life	3 years 9 months 29 days
Options exercisable	41,375
Exercise price, exercisable	$ 37.37
Exercise Price $29.51 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	35,000
Exercise price, outstanding	$ 29.51
Remaining life	9 years 1 month 17 days
Exercise Price $32.50 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	19,825
Exercise price, outstanding	$ 32.50
Remaining life	2 years 1 month 17 days
Exercise Price $36.50 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	19,650
Exercise price, outstanding	$ 36.50
Remaining life	1 year 1 month 17 days
Options exercisable	19,650
Exercise price, exercisable	$ 36.5
Exercise Price $37.26 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	25,350
Exercise price, outstanding	$ 37.26
Remaining life	3 years 1 month 17 days
Exercise Price $38.15 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	21,725
Exercise price, outstanding	$ 38.15
Remaining life	1 month 17 days
Options exercisable	21,725
Exercise price, exercisable	$ 38.15