Note 13 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Notes Tables

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

	2018			2017
Risk–free interest rate		2.46	%		2.08	%
Expected volatility		16.1	%		16.6	%
Expected life, in years		3.0			4.8
Expected dividend yield		3.29	%		3.10	%

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value
Options outstanding at January 1, 2017		177,959		$	55.48	$	–
Options granted		1,125,443			72.96		–
Options exercised		(48,995	)		51.25		–
Options cancelled		(15,000	)		72.94		–
Options outstanding at December 31, 2017		1,239,407			71.19		–
Options granted		111,240			61.40		–
Options exercised		(33,526	)		51.25		–
Options cancelled		(20,000	)		72.94		–
Options outstanding at June 30, 2018		1,297,121		$	70.84	$	2,167,000
Options vested at June 30, 2018		210,881		$	63.35	$	1,613,000

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Options Outstanding June 30, 2018		Exercise Prices			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years
	218,846	$52.93	-	$62.78	$	59.77		2.9
	1,078,275		$72.94			72.94		3.7
	1,297,121				$	70.84		3.6