Retirement Benefits and Trusteed Assets (Details 4) (Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Pension Benefits to be Paid Over the Next 5 Years and Thereafter [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments in 2012	$ 240
Defined Benefit Plan, Expected Future Benefit Payments in 2013	239
Defined Benefit Plan, Expected Future Benefit Payments in 2014	244
Defined Benefit Plan, Expected Future Benefit Payments in 2015	253
Defined Benefit Plan, Expected Future Benefit Payments in 2016	260
Defined Benefit Plan, Expected Future Benefit Payments in 2017-2021	1,439
Total Defined Benefit Pension Plan Expected Future Payments	$ 2,675