Pension Plans and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 30.0	$ 30.2	$ 23.3
Interest cost on benefits earned in prior years	135.1	131.9	138.6
Expected return on plan assets	(192.1)	(181.5)	(156.4)
Amortization of prior service cost (credit)	11.3	13.4	16.6
Amortization of net actuarial loss	71.3	77.4	76.5
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period	0.8	0	0
Total retirement benefit expense	56.4	71.4	98.6
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	3.2	3.1	2.9
Interest cost on benefits earned in prior years	27.5	28.9	32.5
Expected return on plan assets	(1.0)	(1.4)	(1.5)
Amortization of prior service cost (credit)	(18.3)	(18.1)	(19.2)
Amortization of net actuarial loss	9.9	6.0	6.4
Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period	0.2	0	0
Total retirement benefit expense	$ 21.5	$ 18.5	$ 21.1