Components of Other Non-Operating Income (Expense), Net (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Component Of Other Expense Income Nonoperating [Line Items]
FX gain (loss)		$ (16.8)	$ 50.1	$ 1.1
Legacy tax liabilities	$ 1.6		1.6	6.4
Joint venture income		13.3	11.4	11.8
Other		(1.2)	(6.0)	2.0
Other non-operating income (expense), net		$ (4.7)	$ 57.1	$ 21.3