Other Comprehensive Loss - Schedule of Components of Other Comprehensive (Loss) Income and Income Tax (Benefit) Expense Allocated to Each Component (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	$ (3.4)		$ (39.4)		$ (2.5)	$ (16.9)
Other comprehensive loss, Income Tax	(0.9)		0.5		(1.6)	1.5
Other comprehensive loss	(2.5)	$ 1.6	(39.9)	$ 21.5	(0.9)	(18.4)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	(3.2)		(41.6)		(2.0)	(22.7)
Other comprehensive loss	(3.2)		(41.6)		(2.0)	(22.7)
Adjustments for net periodic pension and OPEB cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	(0.2)		2.2		(0.5)	5.8
Other comprehensive loss, Income Tax			0.5		(0.1)	1.5
Other comprehensive loss	(0.2)		$ 1.7		(0.4)	$ 4.3
Other
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Income Tax	(0.9)				(1.5)
Other comprehensive loss	$ 0.9				$ 1.5