Retirement Benefits and Trusteed Assets (Details 3) (Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012
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 2013	$ 236
Defined Benefit Plan, Expected Future Benefit Payments in 2014	242
Defined Benefit Plan, Expected Future Benefit Payments in 2015	252
Defined Benefit Plan, Expected Future Benefit Payments in 2016	260
Defined Benefit Plan, Expected Future Benefit Payments in 2017	269
Defined Benefit Plan, Expected Future Benefit Payments in 2018-2022	1,485
Total Defined Benefit Pension Plan Expected Future Payments	$ 2,744