Fair Value Disclosures - Summary of Non-Pension Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	$ 12.1	$ 14.9
Derivatives, Liabilities	(57.8)	(56.7)
Investment securities, including mutual funds	7.8	8.7
Level 1 [Member] | Fair Value Measurements on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, including mutual funds	5.2	5.2
Level 2 [Member] | Fair Value Measurements on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	12.1	14.9
Derivatives, Liabilities	(57.8)	(56.7)
Investment securities, including mutual funds	$ 2.6	$ 3.5