Pension and Other Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension [Member]
Components of Net Periodic Benefit Expense [Abstract]
Service Cost	$ 2.3	$ 1.9
Interest Cost	6.6	6.9
Expected Return on Plan Assets	(8.8)	(8.7)
Amortization of Prior Service Costs	0.1	0.1
Amortization of Net Loss	4.3	3.0
Net Periodic Benefit Expense	4.5	3.2
Contributions	0	0
Estimated Future Contributions	1.0
Other Postretirement [Member]
Components of Net Periodic Benefit Expense [Abstract]
Service Cost	1.0	1.0
Interest Cost	2.4	2.7
Expected Return on Plan Assets	(2.5)	(2.4)
Amortization of Prior Service Costs	(0.4)	(0.4)
Amortization of Net Loss	1.9	2.1
Net Periodic Benefit Expense	2.4	3.0
Contributions	0	10.9
Estimated Future Contributions	13.9
Prescription Drug Reimbursements	$ 0.3