v2.4.0.8
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (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
Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Balance, beginning of period $ 13 $ 17 $ 16 $ 17  
Included in net income:          
Included in operating revenues 3 [1] (24) [1] 4 [1] (17) [1]  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Gain (Loss) Included In Fuel And Purchased Energy Expense 0 [2] 2 [2] 0 [2] 0 [2]  
Included in OCI 0 0 0 4  
Purchases, issuances and settlements:          
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 0 (1) (1) (1)  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (3) (5) (5) (11)  
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 1 [4] 0 [4] 2 [4] 3 [4]  
Balance, end of period 13 (10) 13 (10)  
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Change in Unrealized Gain (Loss) Held At Period End 3 (22) 4 (17)  
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]          
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure 699   699   1,274
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure $ 172   $ 172   $ 228
[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 each of the three and six months ended June 30, 2013 and 2012.
[4] We had $1 million in gains transferred out of level 3 into level 2 for the three months ended June 30, 2013 and $2 million and $3 million in gains transferred out of level 3 into level 2 for the six months ended June 30, 2013 and 2012, respectively, due to changes in market liquidity in various power markets. There were no transfers out of level 3 into level 2 for the three months ended June 30, 2012.