v2.4.0.6
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance, beginning of period $ 30 $ 38 $ 105
Included in net income:      
Included in operating revenues 5 [1] 7 [1] 14 [1]
Included in fuel and purchased energy expense 0 [2] 0 [2] 5 [2]
Included in OCI 2 2 (4)
Purchases, issuances and settlements:      
Settlements (18) (20) (48)
Transfers into level 3 (2) [3],[4] 0 [3],[4] 0 [3],[4]
Transfers out of level 3 0 [4],[5] 3 [4],[5] (34) [4],[5]
Balance, end of period 17 30 38
Fair Value, Assets Measured with Unobservable Inputs on Recurring Basis, Change in Unrealized Gain (Loss) Held At Period End 5 [2] 7 [2] 19 [2]
Assets and Liabilities with Recurring Fair Value Measurements (Textuals) [Abstract]      
Cash Equivalents Included In Cash And Cash Equivalents, Fair Value Disclosure 1,249 1,094  
Cash Equivalents Included In Restricted Cash, Fair Value Disclosure $ 166 $ 203  
[1] For power contracts and Heat Rate swaps and options, included on our Consolidated Statements of Operations.
[2] For natural gas contracts, swaps and options, included on our Consolidated Statements of Operations.
[3] We had $2 million in losses transferred out of level 2 into level 3 for the year ended December 31, 2011, due to changes in market liquidity in various power and natural gas markets.There were no significant transfers into level 3 for the years ended December 31, 2010 and 2009.
[4] We transfer amounts among levels of the fair value hierarchy as of the end of each period. There were no significant transfers into/out of level 1 during the years ended December 31, 2011, 2010 and 2009.
[5] There were no significant transfers out of level 3 for the year ended 2011. We had $3 million in losses and $(34) million in (gains) transferred out of level 3 into level 2 for the years ended December 31, 2010 and 2009, respectively, due to changes in market liquidity in various power markets.