Other Comprehensive (Loss) Income - Schedule of Components of Other Comprehensive (Loss) Income and Income Tax Expense (Benefit) Allocated to Each Component (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), Before Tax Amount	$ (8.8)			$ 18.9			$ 5.8	$ (9.8)
Other comprehensive income (loss), Income Tax	0.4			0.4			4.1	(3.3)
Other comprehensive (loss) income	(9.2)	$ 17.5	$ (6.6)	18.5	$ 6.2	$ (31.2)	1.7	(6.5)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), Before Tax Amount	(10.4)			17.4			(10.6)	4.2
Other comprehensive (loss) income	(10.4)			17.4			(10.6)	4.2
Adjustments for net periodic pension and OPEB cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), Before Tax Amount	1.4			1.0			4.1	3.0
Other comprehensive income (loss), Income Tax	0.4			0.2			1.0	0.7
Other comprehensive (loss) income	1.0			0.8			3.1	2.3
Changes in Fair Value of Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), Before Tax Amount	0.2			0.5			12.3	(17.0)
Other comprehensive income (loss), Income Tax				0.2			3.1	(4.0)
Other comprehensive (loss) income	$ 0.2			$ 0.3			$ 9.2	$ (13.0)