Other Comprehensive Income (Loss) - Schedule of Components of Other Comprehensive Income (Loss) and Income Tax Expense Allocated to Each Component (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	$ 22.5	$ (31.8)	$ (24.6)
Other comprehensive loss, Income Tax	(0.5)	(9.3)	3.9
Other comprehensive income (loss)	23.0	(22.5)	(28.5)
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	27.8	7.0	(39.9)
Other comprehensive income (loss)	27.8	7.0	(39.9)
Adjustment for net periodic pension and OPEB plan cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	10.3	(39.8)	15.3
Other comprehensive loss, Income Tax	3.1	(9.3)	3.9
Other comprehensive income (loss)	7.2	(30.5)	$ 11.4
Changes in Fair Value of Derivatives
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive loss, Before Tax Amount	(15.6)	1.0
Other comprehensive loss, Income Tax	(3.6)
Other comprehensive income (loss)	$ (12.0)	$ 1.0