Income Taxes - Component of Income Taxes Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Currently payable (refundable):
U.S. federal and state	$ 87.3	$ 35.5	$ 15.1
Non-U.S.	38.5	9.5	3.3
Total	125.8	45.0	18.4
Deferred income taxes (benefit):
U.S. federal and state	(96.9)	(29.1)	(55.8)
Non-U.S.	(148.9)	2.7	144.9
Total	(245.8)	(26.4)	89.1
Provision for income taxes (benefit)	$ (120.0)	$ 18.6	$ 107.5