Retirement Benefits and Trusteed Assets (OPEB - Benefits related to Qualified and Nonqualified Pension Plans Expected to be paid in the Next Ten Years) (Details) (Other Postretirement Benefit Plan, USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
2015	$ 101
2016	107
2017	111
2018	117
2019	122
2020-2024	660
Total Expected Future Benefit Payments	$ 1,218

Retirement Benefits and Trusteed Assets (OPEB - Benefits related to Qualified and Nonqualified Pension Plans Expected to be paid in the Next Ten Years) (Details) (Other Postretirement Benefit Plan, USD $)
In Millions, unless otherwise specified

Dec. 31, 2014