Other Comprehensive Income (Loss) - Schedule of Components of Other Comprehensive Income (Loss) and Income Tax Expense (Benefit) Allocated to Each Component (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	$ 18.9			$ (20.2)			$ (9.8)	$ (22.7)
Other comprehensive (loss) income, Income Tax	0.4			(0.7)			(3.3)	(2.3)
Other comprehensive income (loss)	18.5	$ 6.2	$ (31.2)	(19.5)	$ (2.5)	$ 1.6	(6.5)	(20.4)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	17.4			(19.9)			4.2	(21.9)
Other comprehensive income (loss)	17.4			(19.9)			4.2	(21.9)
Adjustments for net periodic pension and OPEB cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	1.0			(0.3)			3.0	(0.8)
Other comprehensive (loss) income, Income Tax	0.2			(0.1)			0.7	(0.2)
Other comprehensive income (loss)	0.8			(0.2)			2.3	(0.6)
Changes in Fair Value of Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Before Tax Amount	0.5						(17.0)
Other comprehensive (loss) income, Income Tax	0.2						(4.0)
Other comprehensive income (loss)	$ 0.3						$ (13.0)
Other
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive (loss) income, Income Tax				(0.6)				(2.1)
Other comprehensive income (loss)				$ 0.6				$ 2.1