Note 13 - Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	March 31, 2020		December 31, 2019
Risk–free interest rate		1.40%		2.30%
Expected volatility		16.6%		17.4%
Expected life, in years		1.9		2.3
Expected dividend yield		2.55%		2.73%

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value
Options outstanding at January 1, 2019		1,163,381		$	71.16	$	–
Options granted		53,316			77.89		–
Options exercised		(346,168	)		71.57		–
Options cancelled		(85,000	)		72.94		–
Options outstanding at December 31, 2019		785,529			71.24		–
Options granted		57,313			84.46		–
Options exercised		(7,615	)		65.37		–
Options outstanding at March 31, 2020		835,227		$	72.20	$	1,331,000
Options exercisable at March 31, 2020		196,414		$	68.31	$	1,001,000

Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block]

Options Outstanding March 31, 2020	Exercise Prices			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years
133,958	$52.93	-	$62.78		61.80		1.82
701,269	$72.94	-	$86.48		74.19		2.05
835,227					72.20		2.01