Employee Benefits (Components of the Estimated Net Pension and Postretirement Benefits (Income) Expense) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.7	$ 21.3	$ 5.2	$ 64.1
Interest cost	47.5	48.4	142.3	145.4
Expected return on assets	(65.9)	(67.2)	(197.5)	(201.6)
Amortization, net	6.7	12.4	20.6	37.4
Net pension (income) expense	(10.0)	14.9	(29.4)	45.3
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.7	1.8	5.0	6.4
Interest cost	4.7	5.2	13.9	17.6
Expected return on assets	(3.6)	(3.6)	(10.5)	(11.2)
Amortization, net	(5.0)	(5.0)	(14.9)	(7.5)
Net pension (income) expense	$ (2.2)	$ (1.6)	$ (6.5)	$ 5.3