v2.4.0.6
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Balance, beginning of period $ (10) $ 21 $ 17 $ 30  
Included in net income:          
Included in operating revenues 1 [1] (8) [1] 3 [1] (1) [1]  
Included in fuel and purchased energy expense 1 [2] 1 [2] 1 [2] 1 [2]  
Included in OCI 0 (2) 1 3  
Purchases, issuances and settlements:          
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issues (1) 0 (1) 0  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 25 16 (4) (6)  
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 0 [3] 0 [3] 0 [3] 0 [3]  
Transfers out of Level 3 0 [4] 1 [4] 1 [4] 0 [4]  
Balance, end of period 16 27 16 27  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Change in Unrealized Gain (Loss) Held At Period End 2 (7) 4 0  
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]          
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure 1,074   1,074   1,249
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure $ 201   $ 201   $ 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 nine months ended September 30, 2012 and 2011.
[4] We had nil and $1 million in gains transferred out of level 3 into level 2 for the three months ended September 30, 2012 and 2011, respectively. There were $1 million in gains and nil transferred out of level 3 into level 2 for the nine months ended September 30, 2012 and 2011, respectively.