Income Taxes - Components of Income Tax Expense (Benefit) From Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal, Current	$ 60.9	$ (7.3)	$ 8.5
Federal, Deferred	31.0	(51.7)	(11.9)
State, Current	0.2	(6.0)	(8.3)
State, Deferred	(6.0)	12.5	(4.6)
Foreign, Current	26.4	34.4	19.7
Foreign, Deferred	(3.8)	5.8	17.6
Total	$ 108.7	$ (12.3)	$ 21.0