Note 2 - Newly Adopted Accounting Pronouncements - Reconciliation of Allowance for Doubtful Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance at beginning of year		$ 3.6	$ 2.5	$ 2.4
Charged to costs and expenses		2.2	2.5	0.4
Reclassification(1)	[1]	0.0	0.5	0.8
Charged to other accounts(2)	[2]	0.0	0.0	(0.2)
Deductions(3)	[3]	(1.2)	(1.9)	(0.9)
Balance at end of year		$ 4.6	$ 3.6	$ 2.5

[1] Includes amount reclassified between Allowance for Doubtful Accounts and Other Receivables related to a customer's open receivables balance for proper classification and acquisition-related adjustments.

[2] Primarily includes impact from foreign currency fluctuations.

[3] Includes accounts determined to be uncollectible and charged against reserves, net of collections on accounts previously charged against reserves.