Other Comprehensive Income - Schedule of Components of Other Comprehensive Income and Income Tax (Benefit) Expense Allocated to Each Component (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income, Before Tax Amount	$ 0.9	$ 22.5
Other comprehensive income, Income Tax	(0.7)	1.0
Other comprehensive income	1.6	21.5
Translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income, Before Tax Amount	1.2	18.9
Other comprehensive income	1.2	18.9
Adjustment for net periodic pension and OPEB cost
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income, Before Tax Amount	(0.3)	3.6
Other comprehensive income, Income Tax	(0.1)	1.0
Other comprehensive income	(0.2)	$ 2.6
Other
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income, Income Tax	(0.6)
Other comprehensive income	$ 0.6