Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Currently payable
Federal	$ 0.5	$ (0.1)	$ 0.0
International	183.8	125.6	117.7
Total current taxes	184.3	125.5	117.7
Deferred
Federal	0.0	(0.4)	1.2
International	(175.1)	(15.7)	(3.5)
Total deferred taxes	(175.1)	(16.1)	(2.3)
Total provision (benefit) for income taxes	$ 9.2	$ 109.4	$ 115.4