v2.4.0.6
Assets and Liabilities with Recurring Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Transfers into level 3 $ (2) [1],[2] $ 0 [1],[2] $ 0 [1],[2]
Cash equivalents 1,415 [3] 1,297 [3]  
Margin deposits 140 [4] 162 [4]  
Commodity futures contracts 1,043 550  
Commodity forward contracts 111 [5] 341 [5]  
Interest rate swaps 10 4  
Total assets 2,719 2,354  
Margin deposits held by us posted by our counterparties 34 [4],[6] 6 [4],[6]  
Commodity futures contracts 899 574  
Commodity forward contracts 204 [5] 143 [5]  
Interest rate swaps 320 371  
Total liabilities 1,457 1,094  
Transfers out of level 3 0 [2],[7] 3 [2],[7] (34) [2],[7]
Fair Value, Inputs, Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash equivalents 1,415 [3] 1,297 [3]  
Margin deposits 140 162  
Commodity futures contracts 1,043 550  
Commodity forward contracts 0 [5] 0 [5]  
Interest rate swaps 0 0  
Total assets 2,598 2,009  
Margin deposits held by us posted by our counterparties 34 6  
Commodity futures contracts 899 574  
Commodity forward contracts 0 [5] 0 [5]  
Interest rate swaps 0 0  
Total liabilities 933 580  
Fair Value, Inputs, Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash equivalents 0 [3] 0 [3]  
Margin deposits 0 0  
Commodity futures contracts 0 0  
Commodity forward contracts 74 [5] 287 [5]  
Interest rate swaps 10 4  
Total assets 84 291  
Margin deposits held by us posted by our counterparties 0 0  
Commodity futures contracts 0 0  
Commodity forward contracts 184 [5] 119 [5]  
Interest rate swaps 320 371  
Total liabilities 504 490  
Fair Value, Inputs, Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash equivalents 0 [3] 0 [3]  
Margin deposits 0 0  
Commodity futures contracts 0 0  
Commodity forward contracts 37 [5] 54 [5]  
Interest rate swaps 0 0  
Total assets 37 54  
Margin deposits held by us posted by our counterparties 0 0  
Commodity futures contracts 0 0  
Commodity forward contracts 20 [5] 24 [5]  
Interest rate swaps 0 0  
Total liabilities $ 20 $ 24  
[1] 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.
[2] 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.
[3] As of December 31, 2011 and 2010, we had cash equivalents of $1,249 million and $1,094 million included in cash and cash equivalents and $166 million and $203 million included in restricted cash, respectively.
[4] Balances are subject to master netting arrangements and presented on a gross basis on our Consolidated Balance Sheets. We do not offset fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement for financial statement presentation.
[5] Includes OTC swaps and options.
[6] Included in other current liabilities on our Consolidated Balance Sheets.
[7] 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.