Retirement Benefits and Trusteed Assets (Pension Plan - Other Changes in Plan Assets and Benefit Obligations recognized in Reg Assets and OCI) (Details) (Pension Plan, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (581)	$ 395
Amortization of net actuarial loss	(208)	(178)
Total recognized Regulatory assets and Other comprehensive income	(789)	217
Total recognized in net periodic pension cost, Regulatory assets and Other comprehensive income	(561)	437
Future amortization of net actuarial loss into net periodic benefit cost	$ 151	$ 202