Debt - Summary Of Interest Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instruments [Abstract]
Interest incurred	$ 185.0	$ 206.1	$ 211.6
Less: interest income	(2.8)	(4.6)	(3.7)
Less: interest capitalized as property, plant and equipment	(2.6)	(2.8)	(3.8)
Interest expense, net	$ 179.6	$ 198.7	$ 204.1