Note 15 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

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, 2011		1,895,550		$	20.83
Granted		367,000			31.48
Exercised		(363,850	)		19.15
Forfeited		(169,500	)		32.38
Shares issuable under options - December 31, 2012		1,729,200		$	22.31
Granted		422,000			31.35
Exercised		(464,150	)		16.20
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		2.6	$	24,176
Options exercisable - End of period		560,450		$	29.19		1.7	$	12,148

Stock Options Exercised [Table Text Block]

	2014		2013		2012
Number of options exercised		558,150		464,150		363,850
Aggregate fair value	$	27,973	$	16,780	$	11,198
Intrinsic value		17,223		9,313		4,265
Amount of cash received		10,750		7,467		6,933
Tax benefit recognized	$	5,856	$	3,148	$	1,438

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

	2014			2013			2012
Risk free rate		0.9	%		0.4	%		0.4	%
Expected life in years		4.75			4.75			4.75
Expected volatility		25.5	%		37.5	%		40.3	%
Dividend yield		0.8	%		0.0	%		0.0	%
Weighted average fair value per option granted	$	10.52		$	10.13		$	10.87