Note 15 - Stock-based Compensation - Options Outstanding by Exercise Price Range (Details)	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Options outstanding (in shares) | shares	768,851
Weighted average exercise price (in dollars per share)	$ 72.72
Weighted average remaining contractual life (Year)	1 year
Exercise Price Range 1 [Member]
Options outstanding (in shares) | shares	103,775
Exercise price, lower range (in dollars per share)	$ 60.73
Exercise price, upper range (in dollars per share)	67.28
Weighted average exercise price (in dollars per share)	$ 63.65
Weighted average remaining contractual life (Year)	2 years 3 months 18 days
Exercise Price Range 2 [Member]
Options outstanding (in shares) | shares	665,076
Exercise price, lower range (in dollars per share)	$ 71.64
Exercise price, upper range (in dollars per share)	84.30
Weighted average exercise price (in dollars per share)	$ 74.14
Weighted average remaining contractual life (Year)	10 months 24 days