New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 11		$ 50
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)	(17)		5
Net current period other comprehensive income (loss)	(17)		5
Ending balance	(6)		55
Net change in investments tax	12		4
Net actuarial loss tax	0		0
Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)			5
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)	(17)
Amortization of prior service cost	5	[1]	7	[1]
Amortization of net actuarial loss	2	[1]
Transfer to regulatory account	(7)	[1]	(7)	[1]
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(21)		(7)
Amortization of prior service cost	4		5
Amortization of net actuarial loss	3		0
Net current period other comprehensive income (loss)	0		0
Ending balance	(21)		(7)
Pension Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)			0
Net change in investments tax			0
Pension Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)	0
Amortization of prior service cost	2	[1]	3	[1]
Amortization of net actuarial loss	2	[1]
Transfer to regulatory account	(4)	[1]	(3)	[1]
Net change in investments tax	0
Amortization of prior service cost tax	2		2
Net actuarial loss tax	1
Regulatory account transfer	3		2
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	15		15
Amortization of prior service cost	5		6
Amortization of net actuarial loss	1		0
Net current period other comprehensive income (loss)	0		0
Ending balance	15		15
Other Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)			0
Net change in investments tax			0
Other Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)	0
Amortization of prior service cost	3	[1]	4	[1]
Amortization of net actuarial loss	0	[1]
Transfer to regulatory account	(3)	[1]	(4)	[1]
Net change in investments tax	0
Amortization of prior service cost tax	2		2
Net actuarial loss tax	0
Regulatory account transfer	2		2
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	17		42
Net current period other comprehensive income (loss)	(17)		5
Ending balance	0		47
Other Investments [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)			5
Net change in investments tax			4
Other Investments [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments (net of taxes of $0, $0, and $12 in 2015 and $0, $0, and $4 in 2014)	(17)
Amortization of prior service cost	0	[1]	0	[1]
Amortization of net actuarial loss	0	[1]
Transfer to regulatory account	0	[1]	0	[1]
Net change in investments tax	12
Amortization of prior service cost tax	0		0
Net actuarial loss tax	0
Regulatory account transfer	$ 0		$ 0

[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.)