Fair Value Disclosures - Summary of Non-Pension Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	$ 38.5	$ 33.3
Derivatives, Liabilities	(101.6)	(36.8)
Fair Value Measurements on Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Assets	38.5	33.3
Derivatives, Liabilities	(101.6)	(36.8)
Investment securities, including mutual funds	8.7	14.7
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	4.8
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	38.5	33.3
Derivatives, Liabilities	(101.6)	(36.8)
Investment securities, including mutual funds	$ 3.5	$ 9.9