Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, net	$ 2,399.9	$ 2,318.7
Expiration Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	4,753.2	4,246.0
Accumulated amortization	(2,436.7)	(2,004.3)
Amortizable intangible assets, net	2,316.5	2,241.7
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	75.9	68.4
Accumulated amortization	(57.8)	(52.5)
Amortizable intangible assets, net	18.1	15.9
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	107.8	91.8
Accumulated amortization	(42.5)	(30.7)
Amortizable intangible assets, net	$ 65.3	$ 61.1