Note 17 - Share Plans (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	2019			2018			2017
Weighted average grant date fair value	$	19.33		$	17.86		$	16.84
Assumptions:
Expected stock price volatility		33	%		37	%		40	%
Risk free interest rate		2.52	%		2.60	%		1.92	%
Expected annual dividend per share	$	-		$	-		$	-
Expected life of options (years)		6.25			6.25			6.25

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

	Number of Options			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ($ in thousands)
Outstanding as of December 31, 2016		1,482,964		$	27.49		7.5	$	23,840
Granted		346,421			40.13
Exercised		(287,375	)		10.58
Forfeited		(69,880	)		41.12
Outstanding as of December 31, 2017		1,472,130			33.11		7.3	$	25,281
Granted		366,231			43.88
Exercised		(267,909	)		19.90
Forfeited		(49,285	)		43.34
Outstanding as of December 31, 2018		1,521,167			37.70		7.0	$	19,212
Granted		369,779			52.07
Exercised		(263,250	)		30.75
Forfeited		(35,010	)		43.79
Outstanding as of December 31, 2019		1,592,686			42.04		6.9	$	93,242
Exercisable as of December 31, 2019		726,817			37.78		5.3	$	45,649

Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

	Shares			Weighted-Average Grant-Date Fair Value
Non-vested as of December 31, 2016		361,403		$	38.18
Granted		211,769			39.91
Vested		(133,796	)		40.60
Forfeited		(47,100	)		42.48
Non-vested as of December 31, 2017		392,276			37.77
Granted		208,803			44.49
Vested		(128,433	)		39.03
Forfeited		(46,650	)		39.43
Non-vested as of December 31, 2018		425,996			40.50
Granted		265,255			62.38
Vested		(184,628	)		38.78
Forfeited		(14,986	)		44.23
Non-vested as of December 31, 2019		491,637			52.84