Amounts Related to Postretirement Plans Not Reclassified in Entirely out of Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of prior service cost	$ 0.1	[1]	$ 0.3	[1]	$ 0.1	[1]	$ 0.5	[1]
Amortization of actuarial losses	37.3	[1]	47.0	[1]	75.3	[1]	95.3	[1]
Amortization of Curtailment gain	(0.6)	[1]			(0.6)	[1]
Total before tax	36.8		47.3		74.8		95.8
Income tax benefit	(1.5)		(1.9)		(2.9)		(3.7)
Net of tax	$ 35.3		$ 45.4		$ 71.9		$ 92.1

[1] These items are included in net periodic postretirement cost (see note (b)).