New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		$ (7)	$ 11
Change in investments		0	(17)
Net current period other comprehensive income (loss)		0	(17)
Ending balance		(7)	(6)
Net change in investments tax		0	12
Net actuarial loss tax		0	0
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]	3	5
Amortization of net actuarial loss	[1]	5	2
Regulatory account transfer	[1]	(8)	(7)
Change in investments			(17)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		(23)	(21)
Amortization of prior service cost		2	4
Amortization of net actuarial loss		6	3
Net current period other comprehensive income (loss)		0	0
Ending balance		(23)	(21)
Pension Benefits [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]	1	2
Amortization of net actuarial loss	[1]	4	2
Regulatory account transfer	[1]	(5)	(4)
Change in investments			0
Amortization of prior service cost tax		1	2
Net actuarial loss tax		2	1
Regulatory account transfer tax		3	3
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		16	15
Amortization of prior service cost		4	5
Amortization of net actuarial loss		1	1
Net current period other comprehensive income (loss)		0	0
Ending balance		16	15
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
Amortization of net actuarial loss	[1]	1	0
Regulatory account transfer	[1]	(3)	(3)
Change in investments			0
Amortization of prior service cost tax		2	2
Regulatory account transfer tax		2	2
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			17
Net current period other comprehensive income (loss)			(17)
Ending balance			0
Other Investments [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	[1]		0
Amortization of net actuarial loss	[1]		0
Regulatory account transfer	[1]		0
Change in investments			(17)
Change in investments tax		$ 0	$ 12

[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.)