Postretirement Benefits Other Than Pensions - Actuarial Assumptions of OPEB Expense (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member])	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.25%	4.40%	5.25%
Rate of Increase in Future Compensation Levels	2.10%	1.50%	1.50%