v2.4.0.6
Derivative Instruments (Details 2) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Derivatives, Fair Value [Line Items]    
Current derivative assets $ 339 $ 1,051
Long-term derivative assets 98 113
Total derivative assets 437 1,164
Current derivative liabilities 357 1,144
Long-term derivative liabilities 293 279
Total derivative liabilities 650 1,423
Net derivative assets (liabilities) (213) (259)
Fair Value of Derivative Assets 437 1,164
Fair Value of Derivative Liabilities 650 1,423
Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 4 [1] 61 [1]
Fair Value of Derivative Liabilities 184 [1] 167 [1]
Not Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 433 1,103
Fair Value of Derivative Liabilities 466 1,256
Interest Rate Swap [Member]
   
Derivatives, Fair Value [Line Items]    
Current derivative assets 0 0
Long-term derivative assets 4 10
Total derivative assets 4 10
Current derivative liabilities 40 166
Long-term derivative liabilities 160 154
Total derivative liabilities 200 320
Net derivative assets (liabilities) (196) (310)
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 4 [1] 10 [1]
Fair Value of Derivative Liabilities 184 [1] 149 [1]
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 0 0
Fair Value of Derivative Liabilities 16 171
Commodity Option [Member]
   
Derivatives, Fair Value [Line Items]    
Current derivative assets 339 1,051
Long-term derivative assets 94 103
Total derivative assets 433 1,154
Current derivative liabilities 317 978
Long-term derivative liabilities 133 125
Total derivative liabilities 450 1,103
Net derivative assets (liabilities) (17) 51
Commodity Option [Member] | Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 0 [1] 51 [1]
Fair Value of Derivative Liabilities 0 [1] 18 [1]
Commodity Option [Member] | Not Designated as Hedging Instrument [Member]
   
Derivatives, Fair Value [Line Items]    
Fair Value of Derivative Assets 433 1,103
Fair Value of Derivative Liabilities $ 450 $ 1,085
[1] Includes accumulated fair value of derivative instruments as of the date hedge accounting was discontinued, net of amortized fair value for settlement periods which have transpired.