Postretirement Benefits Other Than Pensions - Components Of Comprehensive OPEB (Income) Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Unrecognized Postretirement Benefit Costs Arising During the Year	$ (29.4)	$ (53.9)	$ (27.9)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Benefit Cost, before Tax	(16.2)	(8.7)	(1.2)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost Earned During the Year	0.2	0.1	0.1
Interest Cost on Accumulated Benefit Obligation	1.6	1.9	2.1
Net Amortization and Deferral	(1.2)	(0.6)	(1.1)
Pension Expense Recognized	0.6	1.4	1.1
Unrecognized Postretirement Benefit Costs Arising During the Year	5.5	(4.4)	(4.3)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Benefit Cost, before Tax	1.2	0.6	1.1
Comprehensive OPEB Expense	$ (3.7)	$ 6.4	$ 6.5