Note 6 - Property, Plant and Equipment (Details Textual) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Payments to Acquire Property, Plant, and Equipment, Including Changes in Accrued Expenses Related to Capital Expenditures		$ 257.8	$ 215.8	$ 175.2
Depreciation, Total		$ 197.5	$ 186.0	173.6
Other Noncurrent Assets [Member]
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment				4.6
Headquarters Building and Adjoining Property [Member]
Proceeds from Sale of Property Held-for-sale	$ 6.3			10.1
Gain (Loss) on Disposition of Property Plant Equipment, Total	$ 1.6			$ 6.6