Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal income tax	$ (6.2)	$ 0.4	$ 0.7
State and local income tax	(0.2)	(0.4)	4.9
Foreign income tax	38.8	34.9	27.4
Subtotal	32.4	34.9	33.0
Deferred
Federal income tax	106.2	(9.8)	(36.7)
State and local income tax	(2.7)	(1.3)	(2.6)
Foreign income tax	(11.0)	6.2	8.4
Subtotal	92.5	(4.9)	(30.9)
Total provision for income taxes	$ 124.9	$ 30.0	$ 2.1