Other Comprehensive Income (Loss) - Schedule of Reclassification from Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other operating expense (income)	$ 3.4	$ 5.4	$ 15.5	$ 3.3
Reclassification, net of tax	2.1	(0.2)	4.4	(5.1)
Translation Adjustments
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification, net of tax				(4.5)
Translation Adjustments | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other operating expense (income)				(4.5)
Net Actuarial Loss | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment and other income-net	3.9	1.1	6.9	3.3
Net Prior Service Credit | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment and other income-net	(2.9)	(1.4)	(3.9)	(4.1)
Amortization of Pension and OPEB Cost
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification, net of tax	0.8	(0.2)	2.3	(0.6)
Reclassifications before tax	1.0	(0.3)	3.0	(0.8)
Income tax expense (benefit)	0.2	$ (0.1)	0.7	$ (0.2)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification, net of tax	1.3		2.1
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income | Net Realized Loss on Derivatives
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Interest expense-net	$ 1.3		$ 2.1