v2.4.0.6
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance, beginning of period $ 17 $ 30  
Included in net income:      
Included in operating revenues 10 [1] (6) [1]  
Included in fuel and purchased energy expense (4) [2] 0 [2]  
Included in OCI 4 1  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 1 0  
Purchases, issuances and settlements:      
Settlements (6) (13)  
Transfers into level 3 0 [3],[4] 0 [3],[4]  
Transfers out of level 3 (4) [4],[5] 0 [4],[5]  
Balance, end of period 17 12  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Change in Unrealized Gain (Loss) Held At Period End 6 (6)  
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]      
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure 1,067   1,249
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure 145   166
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis,Asset, Issues $ (1) $ 0  
[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 months ended March 31, 2012 and 2011.
[4] We transfer amounts among levels of the fair value hierarchy as of the end of each period. There were no transfers into/out of level 1 during the three months ended March 31, 2012 and 2011.
[5] We had $4 million of transfers out of level 3 into level 2 for the three months ended March 31, 2012. There were no transfers out of level 3 for the three months ended March 31, 2011.