Income Taxes - Income (Loss) Before Income Taxes and Noncontrolling Interest (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal		$ (32.8)	$ (25.6)	$ (21.8)
International		522.0	586.6	534.3
Income from continuing operations before income taxes		$ 489.2	$ 561.0	$ 512.5
Federal statutory income tax rate	[1]	19.30%	20.00%	20.30%

[1] The statutory rate for 2017, 2016 and 2015 reflects the U.K. statutory rate of 19.3%, 20.0% and 20.3%, respectively.