Note 3 - Revenue 1 (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 1,001.0	$ 1,137.6	$ 1,123.5
Contract with Customer, Liability, Current	$ 5.9	6.8
Short-term Contract with Customer [Member]
Standard Prepaid Maintenance Contract Time Period (Month)	12 months
Long-term Contract with Customer [Member]
Standard Prepaid Maintenance Contract Time Period (Month)	60 months
Equipment Sales [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 629.7	741.8	730.0
Maintenance [Member] | Other Current Liabilities [Member]
Contract with Customer, Liability, Current	5.9	6.8
Maintenance [Member] | Other Liabilities [Member]
Contract with Customer, Liability, Noncurrent	3.4	3.9
Parts and Consumables [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 205.8	221.9	$ 222.3
Revision of Prior Period, Adjustment [Member] | Equipment Sales [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total		(0.9)
Revision of Prior Period, Adjustment [Member] | Parts and Consumables [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total		$ 0.9