Pension and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Service Cost	$ 9.1	$ 7.6	$ 6.2
Interest Cost	26.4	27.4	26.2
Expected Return on Plan Assets	(35.4)	(34.6)	(33.7)
Amortization of Loss	17.5	12.1	6.6
Amortization of Prior Service Cost (Credit)	0.3	0.3	0.5
Net Expense	17.9	12.8	5.8
Postretirement Health and Life [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Service Cost	4.2	3.8	4.8
Interest Cost	9.4	10.8	10.9
Expected Return on Plan Assets	(9.9)	(9.7)	(9.5)
Amortization of Loss	7.5	8.5	4.8
Amortization of Prior Service Cost (Credit)	(1.7)	(1.7)	(0.1)
Amortization of Transition Obligation	0.1	0.1	2.5
Net Expense	$ 9.6	$ 11.8	$ 13.4