Segment Information (Reconciliation Of Total Segment Margin To Net Income (Loss) From Continuing Operations Before Income Taxes) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information
Segment Margin	$ 194	$ 175	$ 347	$ 296
Operation and maintenance	(73)	(57)	(142)	(98)
General and administrative, including related party	(18)	(25)	(51)	(57)
Loss on asset sales, net	1	2	2	2
Depreciation and amortization	(68)	(69)	(133)	(122)
Income (Loss) from Equity Method Investments	(31)	(34)	(66)	(66)
Interest Expense	(41)	(28)	(78)	(57)
Gains (Losses) on Extinguishment of Debt	(7)	(8)	(7)	(8)
Other income and deductions, net	(7)	8	(21)	25	[1]
INCOME (LOSS) BEFORE INCOME TAXES	10	28	(21)	43
Customer Contracts
Segment Reporting Information
Other income and deductions, net				$ 16

[1] Other income and deductions, net for the six months ended June 30, 2012 included a one-time producer payment of $16 million related to an assignment of certain contracts.