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						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	$ (20.2)			$ (6.3)			$ (22.7)	$ (23.2)
Other comprehensive loss, Income Tax	(0.7)			0.5			(2.3)	2.0
Other comprehensive loss	(19.5)	$ (2.5)	$ 1.6	(6.8)	$ (39.9)	$ 21.5	(20.4)	(25.2)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	(19.9)			(8.4)			(21.9)	(31.1)
Other comprehensive loss	(19.9)			(8.4)			(21.9)	(31.1)
Adjustments for net periodic pension and OPEB cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	(0.3)			2.1			(0.8)	7.9
Other comprehensive loss, Income Tax	(0.1)			0.5			(0.2)	2.0
Other comprehensive loss	(0.2)			$ 1.6			(0.6)	$ 5.9
Other
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Income Tax	(0.6)						(2.1)
Other comprehensive loss	$ 0.6						$ 2.1