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Goodwill and Other Intangibles - Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 811.4	$ 585.4
Accumulated Amortization	(122.4)	(113.4)
Net Balance	689.0	472.0
Noncompetition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Amount	4.2	4.2
Accumulated Amortization	(4.1)	(4.1)
Net Balance	0.1	0.1
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Amount	306.7	91.3
Accumulated Amortization	(40.2)	(35.6)
Net Balance	266.5	55.7
Operating Permits
Finite-Lived Intangible Assets [Line Items]
Gross Amount	460.8	460.8
Accumulated Amortization	(51.5)	(48.4)
Net Balance	409.3	412.4
Use Rights And Other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	16.4	16.3
Accumulated Amortization	(13.6)	(13.0)
Net Balance	2.8	3.3
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Amount	23.3	12.8
Accumulated Amortization	(13.0)	(12.3)
Net Balance	$ 10.3	$ 0.5

X

- Definition

Accumulated amount of 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 350
-SubTopic 30
-Section 50
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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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-Name Accounting Standards Codification
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