Income Taxes - Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal, Current	$ 10.4	$ 15.8	$ 60.9
Federal, Deferred	5.4	6.9	31.0
State, Current	0.3	(5.1)	0.2
State, Deferred	7.6	(7.4)	(6.0)
Foreign, Current	24.4	24.5	26.4
Foreign, Deferred	8.5	3.2	(3.8)
Total	$ 56.6	$ 37.9	$ 108.7