Retirement Benefits and Trusteed Assets (Details 12) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011
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 2012	$ 109
Defined Benefit Plan, Expected Future Benefit Payments in 2013	116
Defined Benefit Plan, Expected Future Benefit Payments in 2014	124
Defined Benefit Plan, Expected Future Benefit Payments in 2015	132
Defined Benefit Plan, Expected Future Benefit Payments in 2016	142
Defined Benefit Plan, Expected Future Benefit Payments in 2017-2021	839
Total Expected Future Benefit Payments	$ 1,462