Goodwill and Other Intangibles - Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 880.4	$ 585.4
Accumulated Amortization	(129.2)	(113.4)
Net Balance	751.2	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	312.7	91.3
Accumulated Amortization	(44.3)	(35.6)
Net Balance	268.4	55.7
Operating Permits
Finite-Lived Intangible Assets [Line Items]
Gross Amount	523.8	460.8
Accumulated Amortization	(53.7)	(48.4)
Net Balance	470.1	412.4
Use Rights And Other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	16.4	16.3
Accumulated Amortization	(13.8)	(13.0)
Net Balance	2.6	3.3
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Amount	23.3	12.8
Accumulated Amortization	(13.3)	(12.3)
Net Balance	$ 10.0	$ 0.5