Retirement Benefits and Trusteed Assets (OPEB - Postretirement Cost Inclusions) (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Other Postretirement Costs [Line Items]
Service cost	$ 35	$ 51	$ 49
Interest cost	67	91	91
Expected return on plan assets	(74)	(61)	(62)
Amortization of net loss	47	58	40
Amortization of prior service cost	(100)	(16)	(15)
Amortization of net transition obligation	0	2	2
Net pension or postretirement cost (benefit)	$ (25)	$ 125	$ 105