New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		$ (6)	$ 44	$ 11	$ 50
Change in investments		0	(18)	(17)	(24)
Net current period other comprehensive income (loss)		0	(18)	(17)	(24)
Ending balance		(6)	26	(6)	26
Net change in investments tax		0	13	12	16
Net actuarial loss tax		0	0	0	0
Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments			(4)		6
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]	5	6	15	19
Amortization of net actuarial loss	[1]	2		6	2
Regulatory account transfer	[1]	(7)	(6)	(21)	(21)
Change in investments			(14)	(17)	(30)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		(21)	(7)	(21)	(7)
Amortization of prior service cost		4	5	11	15
Amortization of net actuarial loss		1	1	7	2
Net current period other comprehensive income (loss)		0	0	0	0
Ending balance		(21)	(7)	(21)	(7)
Pension Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments			0		0
Pension Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]	3	3	7	9
Amortization of net actuarial loss	[1]	1		4	1
Regulatory account transfer	[1]	(4)	(3)	(11)	(10)
Change in investments			0	0	0
Amortization of prior service cost tax		1	2	4	6
Net actuarial loss tax		0	0	3	1
Regulatory account transfer tax		3	3	7	7
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		15	15	15	15
Amortization of prior service cost		4	6	14	17
Amortization of net actuarial loss		1	1	3	2
Net current period other comprehensive income (loss)		0	0	0	0
Ending balance		15	15	15	15
Other Benefits [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments			0		0
Other Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]	2	3	8	10
Amortization of net actuarial loss	[1]	1		2	1
Regulatory account transfer	[1]	(3)	(3)	(10)	(11)
Change in investments			0	0	0
Amortization of prior service cost tax		2	3	6	7
Net actuarial loss tax		0	0	1	1
Regulatory account transfer tax		3	4	7	8
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			36	17	42
Net current period other comprehensive income (loss)			(18)	(17)	(24)
Ending balance		0	18	0	18
Other Investments [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments			(4)		6
Net change in investments tax		0	3	0	4
Other Investments [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]		0	0	0
Amortization of net actuarial loss	[1]			0	0
Regulatory account transfer	[1]		0	0	0
Change in investments			(14)	(17)	(30)
Change in investments tax		$ 0	$ 10	$ 12	$ 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.)