Income Taxes - Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
U.S. Federal, Current	$ (4.8)	$ 7.7	$ 7.0
U.S. Federal, Deferred	(5.3)	6.3	10.2
State, Current	(0.7)	0.4	(10.4)
State, Deferred	(5.2)	7.6	(3.2)
Foreign, Current	27.3	24.4	24.7
Foreign, Deferred	(1.3)	8.5	3.2
Total	$ 10.0	$ 54.9	$ 31.5