Note 15 - Stock-based Compensation - Options Outstanding by Exercise Price Range (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares
Weighted Average Exercise Price (in dollars per share)	$ 71.24
Weighted Average Remaining Contractual Life in Years (Year)	2 years 3 months 18 days
Exercise Price Range 1 [Member]
Exercise price, lower range (in dollars per share)	$ 60.73
Exercise price, upper range (in dollars per share)	62.78
Weighted Average Exercise Price (in dollars per share)	$ 61.81
Weighted Average Remaining Contractual Life in Years (Year)	2 years 1 month 6 days
Exercise Price Range 2 [Member]
Exercise price, lower range (in dollars per share)	$ 72.94
Exercise price, upper range (in dollars per share)	77.92
Weighted Average Exercise Price (in dollars per share)	$ 73.29
Weighted Average Remaining Contractual Life in Years (Year)	2 years 3 months 18 days