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	$ 2,863	$ 4,417
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Accumulated benefit obligation, end of year	4,068	4,349
Benefit obligation, beginning of year	4,729	4,195
Service cost	94	82	69
Interest cost	192	204	202
Plan amendments	(3)	0
Actuarial loss	(400)	474
Special termination benefits	0	2	2
Benefits paid	(232)	(228)
Benefit obligation, end of year	4,380	4,729	4,195
Plan assets at fair value, beginning of the year	3,223	2,886
Actual return on plan assets	445	325
Company contributions	284	240
Plan assets at fair value, end of the year	3,720	3,223	2,886
Funded status of the plans	(660)	(1,506)
Current liabilities	(7)	(8)
Noncurrent liabilities	(653)	(1,498)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(660)	(1,506)
Net actuarial loss recognized in other comprehensive loss	174	205
Prior service cost (credit) recognized in other comprehensive income	(1)	(2)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	173	203
Net actuarial loss recognized in regulatory assets	1,654	2,413
Prior service cost recognized in regulatory assets	6	7
Regulatory Assets	$ 1,660	$ 2,420