Components of Estimated Net Pension and Other Postretirement Benefit Plan (Income) Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.5	$ 0.8
Interest cost	47.7	44.6
Expected return on plan assets	(63.1)	(60.6)
Amortization, net	7.8	12.6
Net pension income	(7.1)	(2.6)
Other Postretirement Plan Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.1	1.8
Interest cost	4.2	4.1
Expected return on plan assets	(3.1)	(3.0)
Amortization, net	(6.4)	(4.9)
Net other postretirement benefits plan income	$ (4.2)	$ (2.0)