New And Significant Accounting Policies (Reclassifications Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ (6)	$ 55	$ 11	$ 50
Change in investments	0	(11)	(17)	(6)
Net current period other comprehensive income (loss)	0	(11)	(17)	(6)
Ending balance	(6)	44	(6)	44
Net change in investments tax	0	7	12	3
Net actuarial loss tax	0	0	0	0
Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments		5		10
Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost	5	6	10	13
Amortization of net actuarial loss	2	2	4	2
Transfer to regulatory account	(7)	(8)	(14)	(15)
Realized gain on investments		(16)	(17)	(16)
Pension Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(21)	(7)	(21)	(7)
Amortization of prior service cost	3	5	7	10
Amortization of net actuarial loss	3	1	6	1
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	2	3	4	6
Amortization of net actuarial loss	1	1	3	1
Transfer to regulatory account	(3)	(4)	(7)	(7)
Realized gain on investments		0	0	0
Amortization of prior service cost tax	1	2	3	4
Net actuarial loss tax	2	0	3	0
Regulatory account transfer	3	2	6	4
Other Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	15	15	15	15
Amortization of prior service cost	5	5	10	11
Amortization of net actuarial loss	1	1	2	1
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	3	3	6	7
Amortization of net actuarial loss	1	1	1	1
Transfer to regulatory account	(4)	(4)	(7)	(8)
Realized gain on investments		0	0	0
Amortization of prior service cost tax	2	2	4	4
Net actuarial loss tax	1	0	1	0
Regulatory account transfer	3	2	5	4
Other Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance		47	17	42
Net current period other comprehensive income (loss)		(11)	(17)	(6)
Ending balance	0	36	0	36
Other Investments [Member] | Other Comprehensive Income Before Reclassifications [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Change in investments		5		10
Net change in investments tax	0	3	0	7
Other Investments [Member] | Amounts Reclassified From Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service cost		0	0	0
Amortization of net actuarial loss		0	0	0
Transfer to regulatory account		0	0	0
Realized gain on investments		(16)	(17)	(16)
Change in investments tax	$ 0	$ 10	$ 12	$ 10