Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Currently payable
Federal	[1]	$ (0.1)	$ 0.0	$ 0.0
International	[2]	62.3	76.7	41.5
Total current taxes		62.2	76.7	41.5
Deferred
Federal	[1]	0.0	0.0	0.0
International	[2]	(4.1)	(18.0)	1.2
Total deferred taxes		(4.1)	(18.0)	1.2
Total provision (benefit) for income taxes		$ 58.1	$ 58.7	$ 42.7

[1] (1) “Federal” represents U.K. taxes.

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