Comprehensive Income - Schedule of Reclassification From Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss)
Amortization of pension and other postretirement benefits plan cost:
Reclassifications before tax	[1]	$ 7.8	$ 10.1	$ 23.5	$ 30.5
Accumulated Defined Benefit Plans Adjustment, Net Prior Service
Amortization of pension and other postretirement benefits plan cost:
Reclassifications before tax	[1]	(4.0)	(6.7)	(12.0)	(20.2)
Accumulated Defined Benefit Plans Adjustment, Curtailments
Amortization of pension and other postretirement benefits plan cost:
Reclassifications before tax	[1]	(19.7)		(19.7)
Accumulated Defined Benefit Plans Adjustment, Settlements
Amortization of pension and other postretirement benefits plan cost:
Reclassifications before tax	[1]	1.6		98.5
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Amortization of pension and other postretirement benefits plan cost:
Reclassifications before tax		(14.3)	3.4	90.3	10.3
Income tax (benefit) expense		(7.9)	1.2	35.1	3.7
Reclassifications, net of tax		$ (6.4)	$ 2.2	$ 55.2	$ 6.6

[1] These accumulated other comprehensive income (loss) components are included in the calculation of net periodic pension and other postretirement benefits plan income recognized in cost of sales and selling, general and administrative expenses in the Condensed Consolidated Statements of Operations (see Note 7, Employee Benefits).