Income Taxes - Components of Income Tax Expense (Benefit) From Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal, Current	$ 15.8	$ 60.9	$ (7.3)
Federal, Deferred	6.9	31.0	(51.7)
State, Current	(5.1)	0.2	(6.0)
State, Deferred	(7.4)	(6.0)	12.5
Foreign, Current	24.5	26.4	34.4
Foreign, Deferred	3.2	(3.8)	5.8
Total	$ 37.9	$ 108.7	$ (12.3)