Note 15 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	Number of options			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value
Shares issuable under options - December 31, 2013		1,687,050		$	26.25
Granted		343,000			49.57
Exercised		(558,150	)		19.26
Forfeited		(8,000	)		31.28
Shares issuable under options - December 31, 2014		1,463,900		$	34.35
Granted		698,500			36.61
Exercised		(699,400	)		20.09
Forfeited		(22,500	)		38.71
Shares issuable under options - December 31, 2015		1,440,500		$	28.65
Granted		395,000			32.94
Exercised		(144,150	)		19.83
Forfeited		(88,500	)		32.14
Shares issuable under options - December 31, 2016		1,602,850		$	30.31		2.8	$	11,305
Options exercisable - End of year		510,975		$	25.88		1.9	$	5,777

Stock Options Exercised [Table Text Block]

	2016		2015		2014
Number of options exercised		144,150		699,400		558,150
Aggregate fair value	$	5,222	$	35,516	$	27,973
Intrinsic value		2,364		21,463		17,223
Amount of cash received		2,858		14,053		10,750
Tax benefit recognized	$	-	$	91	$	5,856

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

	2016			2015			2014
Risk-free rate		1.1	%		1.0	%		0.9	%
Expected life in years		4.75			4.75			4.75
Expected volatility		33.0	%		28.6	%		25.5	%
Dividend yield		0.3	%		0.2	%		0.8	%
Weighted average fair value per option granted	$	9.64		$	11.91		$	10.52