New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 55		$ (91)		$ 50		$ (101)
Gain on investments	(11)		16		(6)		22
Net current period other comprehensive income (loss)	(11)		20		(6)		30
Ending balance	44		(71)		44		(71)
Gain on investments tax	7		11		3		15
Net actuarial loss tax	0		3		0		6
Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Gain on investments	5		16		10		22
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	6	[1]	6	[1]	13	[1]	12	[1]
Amortization of net actuarial loss	2	[1]	17	[1]	2	[1]	34	[1]
Transfer to regulatory account	(8)	[1]	(19)	[1]	(15)	[1]	(38)	[1]
Realized gain on investments	(16)				(16)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(7)		(28)		(7)		(28)
Amortization of prior service cost	5		5		10		10
Amortization of net actuarial loss	1		28		1		55
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]
Gain 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]	6	[1]	6	[1]
Amortization of net actuarial loss	1	[1]	16	[1]	1	[1]	32	[1]
Transfer to regulatory account	(4)	[1]	(19)	[1]	(7)	[1]	(38)	[1]
Realized gain on investments	0				0
Amortization of prior service cost tax	2		2		4		4
Net actuarial loss tax	0		12		0		23
Transfer to regulatory account tax	2		13		4		26
Realized gain on investments tax	0				0
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	15		(73)		15		(77)
Amortization of prior service cost	5		5		11		11
Amortization of net actuarial loss	1		2		1		3
Net current period other comprehensive income (loss)	0		4		0		8
Ending balance	15		(69)		15		(69)
Other Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Gain 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]	7	[1]	6	[1]
Amortization of net actuarial loss	1	[1]	1	[1]	1	[1]	2	[1]
Transfer to regulatory account	(4)	[1]	0	[1]	(8)	[1]	0	[1]
Realized gain on investments	0				0
Amortization of prior service cost tax	2		2		4		5
Net actuarial loss tax	0		1		0		1
Transfer to regulatory account tax	2		0		4		0
Realized gain on investments tax	0				0
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	47		10		42		4
Net current period other comprehensive income (loss)	(11)		16		(6)		22
Ending balance	36		26		36		26
Other Investments [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Gain on investments	5		16		10		22
Gain on investments tax	3		11		7		15
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]	0	[1]
Transfer to regulatory account	0	[1]	0	[1]	0	[1]	0	[1]
Realized gain on investments	(16)				(16)
Amortization of prior service cost tax	0		0		0		0
Net actuarial loss tax	0		0		0		0
Transfer to regulatory account tax	0		0		0		0
Realized gain on investments tax	$ 10				$ 10

[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.)