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Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail) - USD ($) $ in Millions | Sep. 30, 2018 | Dec. 31, 2017
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Finite-Lived Intangible Assets [Line Items] |  |  |
Amortizable intangible assets, net | $ 1,772.1 | $ 1,644.6 | [1]
Expiration Lists [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Amortizable intangible assets, gross | 3,342.1 | 3,055.9 |
Accumulated amortization | (1,614.8) | (1,422.1) |
Amortizable intangible assets, net | 1,727.3 | 1,633.8 |
Non-Compete Agreements [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Amortizable intangible assets, gross | 55.9 | 53.5 |
Accumulated amortization | (48.0) | (46.1) |
Amortizable intangible assets, net | 7.9 | 7.4 |
Trade Names [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Amortizable intangible assets, gross | 60.7 | 25.9 |
Accumulated amortization | (23.8) | (22.5) |
Amortizable intangible assets, net | $ 36.9 | $ 3.4 |
[1] | See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to Topic 606.

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