Note 7 - Goodwill and Intangible Assets - Balances of Acquired Intangible Assets, Excluding Goodwill (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Original cost	$ 206.0	$ 218.5
Accumulated amortization	(101.7)	(92.3)
Carrying value	104.3	126.2
Customer Lists [Member]
Original cost	157.7	166.2
Accumulated amortization	(77.7)	(70.3)
Carrying value	$ 80.0	$ 95.9
Weighted average original life (in years) (Year)	15 years	15 years
Trade Names [Member]
Original cost	$ 30.9	$ 34.4
Accumulated amortization	(13.4)	(12.3)
Carrying value	$ 17.5	$ 22.1
Weighted average original life (in years) (Year)	10 years	11 years
Technology-Based Intangible Assets [Member]
Original cost	$ 17.4	$ 17.9
Accumulated amortization	(10.6)	(9.7)
Carrying value	$ 6.8	$ 8.2
Weighted average original life (in years) (Year)	11 years	11 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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