Benefit Plans (Amounts Recognized in Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net actuarial loss (gain)	$ 140.0	$ 131.3
Transition obligation	0.4	0.4
Prior service (credit) cost	(8.8)	(10.2)
Total	131.6	121.5
Other Retirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Net actuarial loss (gain)	2.3	0.2
Transition obligation	0	0
Prior service (credit) cost	0	0.1
Total	$ 2.3	$ 0.3