Pension, Other Postretirement Benefits (OPEB) And Savings Plans (Pre-Tax Changes Recognized In Accumulated Other Comprehensive Income (Loss), Regulatory Assets And Deferred Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period		$ 547	$ 67
Amortization of Net Actuarial Gain (Loss)		(119)	(122)
Prior Service Credit in Current Period		(165)	0
Amortization of Prior Service Credit	19	11	0
Amortization of Transition Asset	0	0	0
Total		274	(55)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Actuarial (Gain) Loss in Current Period		192	48
Amortization of Net Actuarial Gain (Loss)		(14)	(8)
Prior Service Credit in Current Period		(17)	(171)
Amortization of Prior Service Credit		13	(13)
Amortization of Transition Asset		(4)	(27)
Total		$ 170	$ (171)