Pension Plans and Other Postretirement Benefits (Details) (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 - benefits earned during the year	$ 8.8	$ 7.6	$ 26.3	$ 22.5
Interest cost on benefits earned in prior years	33.1	34.6	99.3	100.4
Expected return on plan assets	(45.4)	(49.1)	(136.1)	(142.9)
Amortization of prior service cost (credit)	1.6	2.8	4.8	8.4
Amortization of net actuarial loss	26.3	17.8	78.9	53.5
Total retirement benefit expense	24.4	13.7	73.2	41.9
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	0.8	0.9	2.4	2.3
Interest cost on benefits earned in prior years	6.5	6.9	19.5	20.8
Expected return on plan assets	(0.2)	(0.2)	(0.6)	(0.8)
Amortization of prior service cost (credit)	(4.5)	(4.6)	(13.6)	(13.8)
Amortization of net actuarial loss	3.6	2.5	10.9	7.5
Total retirement benefit expense	$ 6.2	$ 5.5	$ 18.6	$ 16.0