New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 44		$ (71)		$ 50		$ (101)
Loss on investments	(18)		(3)		(24)		19
Net current period other comprehensive income (loss)	(18)		1		(24)		31
Ending balance	26		(70)		26		(70)
Gain on investments tax	13		2		16		13
Net actuarial loss tax	0		3		0		10
Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Loss on investments	(4)		(3)		6		19
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	6	[1]	6	[1]	19	[1]	18	[1]
Amortization of net actuarial loss			18	[1]	2	[1]	52	[1]
Transfer to regulatory account	(6)	[1]	(20)	[1]	(21)	[1]	(58)	[1]
Realized gain on investments	(14)				(30)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(7)		(28)		(7)		(28)
Amortization of prior service cost	5		5		15		15
Amortization of net actuarial loss	1		28		2		83
Net current period other comprehensive income (loss)	0		0		0		0
Ending balance	(7)		(28)		(7)		(28)
Pension Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Loss on investments	0		0		0		0
Gain on investments tax	0		0		0		0
Pension Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	3	[1]	3	[1]	9	[1]	9	[1]
Amortization of net actuarial loss			17	[1]	1	[1]	49	[1]
Transfer to regulatory account	(3)	[1]	(20)	[1]	(10)	[1]	(58)	[1]
Realized gain on investments	0				0
Amortization of prior service cost tax	2		2		6		6
Net actuarial loss tax			11		1		34
Transfer to regulatory account tax	3		13		7		39
Realized gain on investments tax	0				0
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	15		(69)		15		(77)
Amortization of prior service cost	6		6		17		17
Amortization of net actuarial loss	1		1		2		4
Net current period other comprehensive income (loss)	0		4		0		12
Ending balance	15		(65)		15		(65)
Other Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Loss on investments	0		0		0		0
Gain on investments tax	0		0		0		0
Other Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	3	[1]	3	[1]	10	[1]	9	[1]
Amortization of net actuarial loss			1	[1]	1	[1]	3	[1]
Transfer to regulatory account	(3)	[1]	0	[1]	(11)	[1]	0	[1]
Realized gain on investments	0				0
Amortization of prior service cost tax	3		3		7		8
Net actuarial loss tax			0		1		1
Transfer to regulatory account tax	4		0		8		0
Realized gain on investments tax	0				0
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	36		26		42		4
Net current period other comprehensive income (loss)	(18)		(3)		(24)		19
Ending balance	18		23		18		23
Other Investments [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Loss on investments	(4)		(3)		6		19
Gain on investments tax	3		2		4		13
Other Investments [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	0	[1]	0	[1]	0	[1]	0	[1]
Amortization of net actuarial loss			0	[1]	0	[1]	0	[1]
Transfer to regulatory account	0	[1]	0	[1]	0	[1]	0	[1]
Realized gain on investments	(14)				(30)
Amortization of prior service cost tax	0		0		0		0
Net actuarial loss tax			0		0		0
Transfer to regulatory account tax	0		0		0		0
Realized gain on investments tax	$ 10				$ 20

[1] These components are included in the computation of net periodic pension and other postretirement benefit costs. (See the Pension and Other Postretirement Benefits table above for additional details.)