Note 15 - Share Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding, number of options (in shares)	1,472,130	1,482,964	2,128,014
Granted, number of options (in shares)	366,231	346,421	398,313
Exercised, number of options (in shares)	(267,909)	(287,375)	(995,469)
Forfeited, number of options (in shares)	(49,285)	(69,880)	(47,894)
Outstanding, number of options (in shares)	1,521,167	1,472,130	1,482,964	2,128,014
Exercisable, number of options (in shares)	696,954
Outstanding, weighted average exercise price (in dollars per share)	$ 33.11	$ 27.49	$ 15.15
Granted, weighted average exercise price (in dollars per share)	43.88	40.13	33.24
Exercised, weighted average exercise price (in dollars per share)	19.90	10.58	2.89
Forfeited, weighted average exercise price (in dollars per share)	43.34	41.12	37.41
Outstanding, weighted average exercise price (in dollars per share)	37.70	$ 33.11	$ 27.49	$ 15.15
Exercisable, weighted average exercise price (in dollars per share)	$ 34.16
Outstanding, weighted average remaining contractual term (Year)	7 years	7 years 109 days	7 years 182 days	7 years 255 days
Exercisable, weighted average remaining contractual term (Year)	5 years 219 days
Outstanding, aggregate intrinsic value	$ 19,212	$ 25,281	$ 23,840	$ 40,271
Exercisable, aggregate intrinsic value	$ 11,779