Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Currently payable
Federal	[1]	$ 0.1	$ 0.0	$ (0.1)
International	[2]	70.3	64.2	62.3
Total current taxes		70.4	64.2	62.2
Deferred
International	[2]	4.6	(18.4)	(4.1)
Total deferred taxes		4.6	(18.4)	(4.1)
Total provision (benefit) for income taxes		$ 75.0	$ 45.8	$ 58.1

[1] “Federal” represents U.K. taxes.

[2] “International” represents non-U.K. taxes.