Accumulated Other Comprehensive Income - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense), net	$ (3.2)	$ 2.6	$ (11.6)	$ 1.4
Total reclassification for the period	38.0	36.5	72.9	72.3
Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total reclassification for the period			(5.1)
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of postretirement plan items, before tax	(1.4)	(1.4)	(2.8)	(2.8)
Amortization of actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of postretirement plan items, before tax	44.9	39.4	88.2	78.0
Curtailment gain
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of postretirement plan items, before tax	(5.2)	0.0	(5.2)	0.0
Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of postretirement plan items, before tax	38.5	38.0	75.1	75.2
Income tax benefit	(0.5)	(1.5)	(2.2)	(2.9)
Total reclassification for the period			78.0
Adjustment for substantial completion of liquidation of foreign subsidiaries | Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income (expense), net	$ 0.2	$ 0.0	$ (5.1)	$ 0.0