Income Taxes - Income (Loss) Before Income Taxes and Noncontrolling Interest (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Federal	[1]	$ 7.2	$ (1.6)	$ (24.6)
International	[2]	424.9	409.1	404.4
Income from continuing operations before income taxes		$ 432.1	$ 407.5	$ 379.8
Federal statutory income tax rate		19.00%	19.00%	19.00%

[1] “Federal” reflects United Kingdom (“U.K.”) income (loss) from continuing operations before income taxes.

[2] “International” reflects non-U.K. income from continuing operations before income taxes.