Fair Value Measurement of Assets and Liabilities - Fair Value Measurements of Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 73.4	$ 6.1
Contingent payments related to acquisitions	21.2	41.0
Total Liabilities	26.5	91.9
Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	73.4	6.1
Total Liabilities	5.3	50.9
Fair Value Measurements at Reporting Date Using: Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payments related to acquisitions	21.2	41.0
Total Liabilities	21.2	41.0
Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, current and long-term	38.1	1.6
Derivatives, current and long-term	1.3	50.9
Foreign Exchange Forward Contracts [Member] | Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, current and long-term	38.1	1.6
Derivatives, current and long-term	1.3	50.9
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, current and long-term	35.3	4.5
Derivatives, current and long-term	4.0
Interest Rate Swaps [Member] | Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, current and long-term	35.3	$ 4.5
Derivatives, current and long-term	$ 4.0