Note 16 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

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

	Year Ended December 31,
	2020			2019			2018
Risk–free interest rate		0.87	%		2.30	%		2.46	%
Expected volatility		20.1	%		17.4	%		16.1	%
Expected life, in years		2.2			2.3			3.0
Expected dividend yield		2.91	%		2.73	%		3.29	%

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

	Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value
Options outstanding at January 1, 2018		1,239,407			71.19		−
Options granted		110,265			61.39		−
Options exercised		(68,291	)		54.31		−
Options cancelled		(118,000	)		72.11		−
Options outstanding at December 31, 2018		1,163,381			71.16		−
Options granted		77,316			77.89		−
Options exercised		(346,168	)		71.57		−
Options cancelled		(85,000	)		72.94		−
Options outstanding at December 31, 2019		809,529			71.24		−
Options granted		104,057			73.98		−
Options exercised		(43,630	)		63.37		−
Options cancelled		(3,000	)		72.94		−
Options outstanding at December 31, 2020		866,956		$	72.11	$	572,790
Options exercisable at December 31, 2020		215,456		$	68.35	$	572,790

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

Options Outstanding December 31, 2020	Exercise Prices			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years
153,000	$60.73	–	64.64	$	62.67		2.3
713,956	$72.94	–	$84.30		74.14		1.3
866,956				$	72.11		1.3