Note 1 - Nature of Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Fair value assumptions for stock option grants and stock purchase grants

	2023		2022		2021
Dividend yield		0.45%		0.43% to 0.45%		0.55%
Expected volatility		22.31%		22.65% to 23.52%		23.57%
Risk-free interest rate		4.22%		1.87% to 3.12%		1.62%
Expected life of option grants		6.25 years		6.25 years		6.25 years
Weighted-average grant date fair value	$	16.36	$	13.94 to 15.09	$	10.85

	2023		2022		2021
Dividend yield		0.48% to 0.58%		0.43% to 0.44%		0.49% to 0.61%
Expected volatility		15.86% to 29.69%		17.97% to 21.16%		37.51% to 38.65%
Risk-free interest rate		4.67% to 5.47%		0.14% to 2.24%		0% to 0.06%
Expected life of purchase grants		3 to 6 months		3 to 6 months		3 to 6 months
Weighted-average grant date fair value	$	8.35	$	7.88	$	7.67