Derivatives and Financial Instruments - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	$ 8.8
Foreign Currency Contracts, Liability, Fair Value Disclosure	(47.2)	$ (39.8)
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract assets	0.6
Foreign Currency Contracts, Liability, Fair Value Disclosure	(47.2)	(39.8)
Deferred compensation plan	23.2	24.9
Derivative Assets (Liabilities), at Fair Value, Net	(23.4)	(14.9)
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract assets	0.0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0.0	0.0
Deferred compensation plan	18.7	21.2
Derivative Assets (Liabilities), at Fair Value, Net	18.7	21.2
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract assets	0.6
Foreign Currency Contracts, Liability, Fair Value Disclosure	(47.2)	(39.8)
Deferred compensation plan	4.5	3.7
Derivative Assets (Liabilities), at Fair Value, Net	(42.1)	(36.1)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract assets	0.0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0.0	0.0
Deferred compensation plan	0.0	0.0
Derivative Assets (Liabilities), at Fair Value, Net	$ 0.0	$ 0.0