Note 15 - Share Plans - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Outstanding, number of options (in shares)	2,128,014	2,542,139	2,937,301
Outstanding, weighted average exercise price (in dollars per share)	$ 15.15	$ 9.94	$ 5.74
Outstanding, weighted average remaining contractual term (Year)	7 years 182 days	7 years 255 days	8 years 182 days	9 years 182 days
Outstanding, aggregate intrinsic value	$ 23,840	$ 40,271	$ 96,518	$ 148,369
Granted, number of options (in shares)	398,313	287,165	187,189
Granted, weighted average exercise price (in dollars per share)	$ 33.24	$ 45.18	$ 57.21
Exercised, number of options (in shares)	(995,469)	(604,088)	(549,282)
Exercised, weighted average exercise price (in dollars per share)	$ 2.89	$ 3.79	$ 3.44
Expired, number of options (in shares)		(6,409)	(259)
Expired, weighted average exercise price (in dollars per share)		$ 50.11	$ 15.94
Forfeited, number of options (in shares)	(47,894)	(90,793)	(32,810)
Forfeited, weighted average exercise price (in dollars per share)	$ 37.41	$ 37.27	$ 12.68
Outstanding, number of options (in shares)	1,482,964	2,128,014	2,542,139	2,937,301
Outstanding, weighted average exercise price (in dollars per share)	$ 27.49	$ 15.15	$ 9.94	$ 5.74
Exercisable, number of options (in shares)	787,654
Exercisable, weighted average exercise price (in dollars per share)	$ 17.64
Exercisable, weighted average remaining contractual term (Year)	6 years 255 days
Exercisable, aggregate intrinsic value	$ 19,897