Other Comprehensive Loss - Schedule of Reclassification From Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification, net of tax	$ (0.2)	$ 1.0	$ (5.1)	$ 4.1
Other operating expense (income)	5.4	(4.5)	3.3	(4.6)
Investment and other income-net	4.6	5.5	11.3	14.7
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	1.1	2.0	3.3	5.9
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	(1.4)	(0.8)	(4.1)	(2.2)
Settlements | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment and other income-net		0.2		1.5
Amortization of Pension and OPEB Cost
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassifications before tax	(0.3)	1.4	(0.8)	5.2
Income tax benefit	(0.1)	0.4	(0.2)	1.1
Reclassification, net of tax	$ (0.2)	$ 1.0	$ (0.6)	$ 4.1