Retirement Benefits and Trusteed Assets (OPEB - Other Changes in Plan Assets and APBO Recognized in Regulatory Assets and OCI) (Details) (Other Postretirement Benefit Plan, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (353)	$ (34)
Amortization of net actuarial loss	(64)	(80)
Prior service credit	(218)	(264)
Amortization of prior service cost	131	27
Amortization of transition asset	0	(2)
Total recognized Regulatory assets and Other comprehensive income	(504)	(353)
Total recognized in net periodic pension cost, Regulatory assets and Other comprehensive icnome	(546)	(202)
Future amortization of net actuarial loss into net periodic benefit cost	21	69
Future amortization of prior service credit into net periodic benefit cost	$ (144)	$ (91)