Note 15 - Share-based Payments - Summary of Exercise Prices, Weighted Average Remaining Contractual Life and Intrinsic Values of Outstanding Options (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Options outstanding, Number outstanding (in shares) | shares	730,037
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 50.85
Options outstanding, Weighted average remaining contractual life (Year)	4 years 73 days
Options outstanding, Aggregate intrinsic value | $	$ 4,070
Options Exercisable, Number exercisable (in shares) | shares	349,845
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 41.65
Options Exercisable, Weighted average remaining contractual life (Year)	3 years 36 days
Options Exercisable, Aggregate intrinsic value | $	$ 4,046
Exercise Price Range 01 [Member]
Exercise price - lower (in dollars per share)	$ 8.56
Exercise price - higher (in dollars per share)	$ 8.56
Options outstanding, Number outstanding (in shares) | shares	15,722
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 8.56
Options outstanding, Weighted average remaining contractual life (Year)	36 days
Options outstanding, Aggregate intrinsic value | $	$ 624
Options Exercisable, Number exercisable (in shares) | shares	15,722
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 8.56
Options Exercisable, Weighted average remaining contractual life (Year)	36 days
Options Exercisable, Aggregate intrinsic value | $	$ 624
Exercise Price Range 02 [Member]
Exercise price - lower (in dollars per share)	$ 10.16
Exercise price - higher (in dollars per share)	$ 19.95
Options outstanding, Number outstanding (in shares) | shares	62,990
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 16.23
Options outstanding, Weighted average remaining contractual life (Year)	1 year 182 days
Options outstanding, Aggregate intrinsic value | $	$ 2,018
Options Exercisable, Number exercisable (in shares) | shares	62,990
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 16.23
Options Exercisable, Weighted average remaining contractual life (Year)	1 year 182 days
Options Exercisable, Aggregate intrinsic value | $	$ 2,018
Exercise Price Range 03 [Member]
Exercise price - lower (in dollars per share)	$ 21.10
Exercise price - higher (in dollars per share)	$ 27.53
Options outstanding, Number outstanding (in shares) | shares	51,250
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 24.11
Options outstanding, Weighted average remaining contractual life (Year)	1 year 255 days
Options outstanding, Aggregate intrinsic value | $	$ 1,237
Options Exercisable, Number exercisable (in shares) | shares	51,250
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 24.11
Options Exercisable, Weighted average remaining contractual life (Year)	1 year 255 days
Options Exercisable, Aggregate intrinsic value | $	$ 1,237
Exercise Price Range 04 [Member]
Exercise price - lower (in dollars per share)	$ 35.25
Exercise price - higher (in dollars per share)	$ 37.35
Options outstanding, Number outstanding (in shares) | shares	14,375
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 35.89
Options outstanding, Weighted average remaining contractual life (Year)	3 years 73 days
Options outstanding, Aggregate intrinsic value | $	$ 178
Options Exercisable, Number exercisable (in shares) | shares	13,125
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 35.95
Options Exercisable, Weighted average remaining contractual life (Year)	3 years 36 days
Options Exercisable, Aggregate intrinsic value | $	$ 162
Exercise Price Range 05 [Member]
Exercise price - lower (in dollars per share)	$ 44.90
Exercise price - higher (in dollars per share)	$ 47
Options outstanding, Number outstanding (in shares) | shares	10,000
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 46.95
Options outstanding, Weighted average remaining contractual life (Year)	5 years 146 days
Options outstanding, Aggregate intrinsic value | $	$ 13
Options Exercisable, Number exercisable (in shares) | shares	3,750
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 47
Options Exercisable, Weighted average remaining contractual life (Year)	4 years
Options Exercisable, Aggregate intrinsic value | $	$ 5
Exercise Price Range 06 [Member]
Exercise price - lower (in dollars per share)	$ 51.82
Exercise price - higher (in dollars per share)	$ 58.65
Options outstanding, Number outstanding (in shares) | shares	337,353
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 55.53
Options outstanding, Weighted average remaining contractual life (Year)	4 years 73 days
Options outstanding, Aggregate intrinsic value | $
Options Exercisable, Number exercisable (in shares) | shares	176,527
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 55.69
Options Exercisable, Weighted average remaining contractual life (Year)	4 years
Options Exercisable, Aggregate intrinsic value | $
Exercise Price Range 07 [Member]
Exercise price - lower (in dollars per share)	$ 61.33
Exercise price - higher (in dollars per share)	$ 64.10
Options outstanding, Number outstanding (in shares) | shares	238,347
Options outstanding, Weighted average exercise price per share (in dollars per share)	$ 62.99
Options outstanding, Weighted average remaining contractual life (Year)	5 years 255 days
Options outstanding, Aggregate intrinsic value | $
Options Exercisable, Number exercisable (in shares) | shares	26,481
Options Exercisable, Weighted average exercise price per share (in dollars per share)	$ 64.10
Options Exercisable, Weighted average remaining contractual life (Year)	5 years 73 days
Options Exercisable, Aggregate intrinsic value | $