Comprehensive Income - Schedule of Reclassification From Accumulated Other Comprehensive Income (Loss) (Detail) (Pension and Other Postretirement Benefit Plan Cost, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Pension and Other Postretirement Benefit Plan Cost
Amortization of pension and other postretirement benefits plan cost:
Net actuarial loss	$ 31.9	[1]	$ 50.5	[1]	$ 32.0	[1]
Net prior service credit	(25.8)	[1]	(19.7)	[1]	(19.1)	[1]
Curtailments and settlements	95.7	[1]	0.7	[1]	(2.6)	[1]
Reclassifications before tax	101.8		31.5		10.3
Income tax expense	39.3		11.7		3.9
Reclassifications, net of tax	$ 62.5		$ 19.8		$ 6.4

[1] These accumulated other comprehensive (loss) income components are included in the calculation of net periodic pension and other postretirement benefits plan (income) expense recognized in cost of sales and selling, general and administrative expenses in the Consolidated Statements of Operations (see Note 11).