Note 9 - Share-based Compensation - Stock Options Valuation Assumptions (Details) - Common Stock [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Expected dividend yield at date of grant	2.13%	3.39%	2.15%
Expected stock price volatility	35.12%	35.52%	34.85%
Risk-free interest rate	3.61%	2.33%	0.91%
Expected life of options (in years) (Year)	6 years 10 months 6 days	6 years 3 months 14 days	7 years 3 days