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Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, net	$ 1,731.0	$ 1,644.6	[1]
Expiration Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	3,233.4	3,055.9
Accumulated amortization	(1,547.5)	(1,422.1)
Amortizable intangible assets, net	1,685.9	1,633.8
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	54.9	53.5
Accumulated amortization	(47.4)	(46.1)
Amortizable intangible assets, net	7.5	7.4
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	60.6	25.9
Accumulated amortization	(23.0)	(22.5)
Amortizable intangible assets, net	$ 37.6	$ 3.4
[1] See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to ASC 606.

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