Retirement Benefits and Trusteed Assets (OPEB - Other Changes in Plan Assets and APBO Recognized in Regulatory Assets and OCI) (Details) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (258)	$ (14)
Amortization of net actuarial loss	(47)	(58)
Prior service credit	(159)	(207)
Amortization of prior service cost	100	16
Amortization of transition (asset)	0	(2)
Total recognized Regulatory assets and Other comprehensive income	(364)	(265)
Total recognized in net periodic pension cost, Regulatory assets and Other comprehensive icnome	(389)	(140)
Net actuarial loss	15	50
Prior service credit	$ (109)	$ (69)