Derivatives and Financial Instruments - Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract liabilities	$ (1.9)	$ (30.6)
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contract assets	0.2
Foreign currency contract liabilities	(1.9)	(30.6)
Deferred compensation plan	20.0	20.9
Total recurring fair value measurements	18.3	(9.7)
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 contract liabilities	0.0	0.0
Deferred compensation plan	11.6	17.6
Total recurring fair value measurements	11.6	17.6
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	0.2
Foreign currency contract liabilities	(1.9)	(30.6)
Deferred compensation plan	0.0	0.0
Total recurring fair value measurements	(1.7)	(30.6)
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 contract liabilities	0.0	0.0
Deferred compensation plan	0.0	0.0
Total recurring fair value measurements	0.0	0.0
Fair Value Measured at Net Asset Value Per Share [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 contract liabilities	0.0	0.0
Deferred compensation plan	8.4	3.3
Total recurring fair value measurements	$ 8.4	$ 3.3