Retirement Benefits and Trusteed Assets (Details 11) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
Benefits Expected to be Paid Over the Next Five Years and Thereafter [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in 2013	$ 103
Defined Benefit Plan, Expected Future Benefit Payments in 2014	109
Defined Benefit Plan, Expected Future Benefit Payments in 2015	115
Defined Benefit Plan, Expected Future Benefit Payments in 2016	120
Defined Benefit Plan, Expected Future Benefit Payments in 2017	127
Defined Benefit Plan, Expected Future Benefit Payments in 2018-2022	726
Total Expected Future Benefit Payments	$ 1,300