v2.4.0.6
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Balance, beginning of period $ 17 $ 12 $ 17 $ 30  
Included in net income:          
Included in operating revenues (24) [1] 10 [1] (17) [1] 6 [1]  
Included in fuel and purchased energy expense 2 [2] 1 [2] 0 [2] 0 [2]  
Included in OCI 0 4 4 5  
Purchases, issuances and settlements:          
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  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 1 1 1 1  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issues (1) 0 (1) 0  
Settlements (5) (7) (11) (21)  
Transfers into level 3 0 [3] 0 [3] 0 [3] 0 [3]  
Transfers out of level 3 0 [4] 0 [4] (3) [4] 0 [4]  
Balance, end of period (10) 21 (10) 21  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Change in Unrealized Gain (Loss) Held At Period End (22) 11 (17) 7  
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]          
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure 574   574   1,249
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure $ 149   $ 149   $ 166
[1] For power contracts and Heat Rate swaps and options, 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] There were no transfers out of level 2 into level 3 for the three and six months ended June 30, 2012 and 2011.
[4] We had $3 million of transfers out of level 3 into level 2 for the six months ended June 30, 2012. There were no transfers out of level 3 for the three months ended June 30, 2012 and for the three and six months ended June 30, 2011.