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	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares
Number outstanding (in shares) | shares	956,234
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 62.88
Weighted average remaining contractual life, options outstanding (Year)	4 years 7 months 6 days
Aggregate intrinsic value, options outstanding | $	$ 15,479
Number exercisable (in shares) | shares	470,317
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 54.87
Weighted average remaining contractual life, options exercisable (Year)	3 years 2 months 12 days
Aggregate intrinsic value, options exercisable | $	$ 11,326
Exercise Price Range 01 [Member]
Number outstanding (in shares) | shares	24,500
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 19.56
Weighted average remaining contractual life, options outstanding (Year)	7 months 6 days
Aggregate intrinsic value, options outstanding | $	$ 1,455
Number exercisable (in shares) | shares	24,500
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 19.56
Weighted average remaining contractual life, options exercisable (Year)	7 months 6 days
Aggregate intrinsic value, options exercisable | $	$ 1,455
Exercise Price Range 02 [Member]
Number outstanding (in shares) | shares	20,892
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 21.10
Weighted average remaining contractual life, options outstanding (Year)	1 year 3 months 18 days
Aggregate intrinsic value, options outstanding | $	$ 1,209
Number exercisable (in shares) | shares	20,892
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 21.10
Weighted average remaining contractual life, options exercisable (Year)	1 year 3 months 18 days
Aggregate intrinsic value, options exercisable | $	$ 1,209
Exercise Price Range 03 [Member]
Number outstanding (in shares) | shares	4,375
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 37.35
Weighted average remaining contractual life, options outstanding (Year)	3 months 18 days
Aggregate intrinsic value, options outstanding | $	$ 182
Number exercisable (in shares) | shares	4,375
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 37.35
Weighted average remaining contractual life, options exercisable (Year)	3 months 18 days
Aggregate intrinsic value, options exercisable | $	$ 182
Exercise Price Range 04 [Member]
Number outstanding (in shares) | shares	13,000
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 47.36
Weighted average remaining contractual life, options outstanding (Year)	4 years 3 months 18 days
Aggregate intrinsic value, options outstanding | $	$ 411
Number exercisable (in shares) | shares	7,000
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 47.29
Weighted average remaining contractual life, options exercisable (Year)	3 years 3 months 18 days
Aggregate intrinsic value, options exercisable | $	$ 222
Exercise Price Range 05 [Member]
Number outstanding (in shares) | shares	253,656
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 55.57
Weighted average remaining contractual life, options outstanding (Year)	2 years 9 months 18 days
Aggregate intrinsic value, options outstanding | $	$ 5,930
Number exercisable (in shares) | shares	239,131
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 55.59
Weighted average remaining contractual life, options exercisable (Year)	2 years 8 months 12 days
Aggregate intrinsic value, options exercisable | $	$ 5,586
Exercise Price Range 06 [Member]
Number outstanding (in shares) | shares	360,661
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 62.02
Weighted average remaining contractual life, options outstanding (Year)	4 years 9 months 18 days
Aggregate intrinsic value, options outstanding | $	$ 6,107
Number exercisable (in shares) | shares	164,219
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 63.07
Weighted average remaining contractual life, options exercisable (Year)	4 years 6 months
Aggregate intrinsic value, options exercisable | $	$ 2,607
Exercise Price Range 07 [Member]
Number outstanding (in shares) | shares	279,150
Weighted average exercise price per share, options outstanding (in dollars per share) | $ / shares	$ 78.69
Weighted average remaining contractual life, options outstanding (Year)	6 years 4 months 24 days
Aggregate intrinsic value, options outstanding | $	$ 185
Number exercisable (in shares) | shares	10,200
Weighted average remaining contractual life, options exercisable (in dollars per share) | $ / shares	$ 72.64
Weighted average remaining contractual life, options exercisable (Year)	6 years 2 months 12 days
Aggregate intrinsic value, options exercisable | $	$ 65