Retirement Benefits and Trusteed Assets (Pension Plan - Reconciliation of Obligations, Assets and Funded Status of Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Regulatory Assets	$ 2,288	$ 3,510
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Accumulated benefit obligation, end of year	3,111	3,307
Projected benefit obligation, beginning of year	3,585	3,196
Service cost	73	64	55
Interest cost	146	155	154
Actuarial loss	(286)	342
Settlements	0	2	2
Benefits paid	(177)	(174)
Projected benefit obligation, end of year	3,341	3,585	3,196
Plan assets at fair value, beginning of the yeard Benefit Plan, Fair Value of Plan Assets	2,211	1,957
Actual return on plan assets	316	220
Company contributions	282	208
Plan assets at fair value, end of the yeard Benefit Plan, Fair Value of Plan Assets	2,632	2,211	1,957
Funded status of the plan	(709)	(1,374)
Current liabilities	(4)	(6)
Noncurrent liabilities	(705)	(1,368)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(709)	(1,374)
Net actuarial loss	1,248	1,805
Prior service cost	9	10
Regulatory Assets	$ 1,257	$ 1,815