Postretirement Benefits Other Than Pensions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Postretirement Benefit Plan, Number of Retired Employees Covered	600
Other Postretirement Benefit Plan, Number of Active Employees Covered	400
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	$ 2.8	$ 2.8
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	0.1	0.1
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year	1.0
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 4.3
Medical Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year	7.00%	7.50%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Future Years	5.00%	5.00%
Prescription Drug Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year	8.50%	9.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Future Years	5.00%	5.00%