Note 11 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Notes Tables

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

	2016			2015
Risk–free interest rate		0.88	%		0.71	%
Expected volatility		15.8	%		16.5	%
Expected life, in years		2.2			2.2
Expected dividend yield		3.08	%		2.73	%

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

	Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value
Options outstanding at January 1, 2015		954,678		$	46.92	$	–
Options granted		56,210			61.47		–
Options exercised		(389,498	)		47.06		–
Options outstanding at December 31, 2015		621,390			48.15		–
Options granted		57,120			62.53		–
Options exercised		(480,275	)		46.81		–
Options forfeited		(656	)		46.69		–
Options outstanding at June 30, 2016		197,579		$	55.55	$	1,816,000
Options exercisable at June 30, 2016		185,459		$	55.15	$	1,778,000

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

Options Outstanding June 30, 2016	Exercise Prices			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years
97,500	$4.80	-	$52.93	$	48.95		2.0
100,079	$1.59	-	$62.78		61.98		3.9
197,579				$	55.55		3.0