Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 8		$ 13		$ 14		$ 16
Included in net income:
Included in operating revenues	(7)	[1]	3	[1]	(15)	[1]	4	[1]
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense	0	[2]	0	[2]	6	[2]	0	[2]
Purchases, issuances and settlements:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		1		0		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0		0		0		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(3)		(3)		(6)		(5)
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0		0		0		0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0		0		0		0
Transfers into level 3	2	[3],[4]	0	[3],[4]	0	[3],[4]	0	[3],[4]
Transfers out of Level 3	(9)	[4],[5]	(1)	[4],[5]	(8)	[4],[5]	(2)	[4],[5]
Balance, end of period	(9)		13		(9)		13
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(7)		3		(9)		4
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure	406				406				889
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure	$ 230				$ 230				$ 245

[1] For power contracts and other power-related products, included on our Consolidated Condensed Statements of Operations.

[2] For natural gas contracts, swaps and options, included on our Consolidated Condensed Statements of Operations.

[3] We had $2 million in gains transferred out of level 2 into level 3 for the three months ended June 30, 2014 due to changes in market liquidity in various power markets. There were no transfers out of level 2 into level 3 for the three months ended June 30, 2013 and for each of the six months ended June 30, 2014 and 2013.

[4] We transfer amounts among levels of the fair value hierarchy as of the end of each period. There were no transfers into or out of level 1 for each of the three and six months ended June 30, 2014 and 2013.

[5] We had $9 million and $1 million in gains transferred out of level 3 into level 2 for the three months ended June 30, 2014 and 2013, respectively, and $8 million and $2 million in gains transferred out of level 3 into level 2 for the six months ended June 30, 2014 and 2013, respectively, due to changes in market liquidity in various power markets.