v3.3.1.900
Derivative Instruments (Details 2) (Details) - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Derivatives, Fair Value [Line Items]    
Derivative Assets, Current $ 1,698 $ 2,058
Long-term derivative assets 313 439
Total derivative assets 2,011 2,497
Derivative Liabilities, current 1,734 1,782
Long-term derivative liabilities 473 444
Derivative Liability, Fair Value, Gross Liability 2,207 2,226
Net derivative assets (liabilities) (196) 271
Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Total derivative assets 1 4
Derivative Liability, Fair Value, Gross Liability 92 112
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Total derivative assets 2,010 2,493
Derivative Liability, Fair Value, Gross Liability 2,115 2,114
Energy Related Derivative [Member]    
Derivatives, Fair Value [Line Items]    
Derivative assets, current 1,698 2,058
Derivative Asset, Noncurrent 312 435
Total derivative assets 2,010 2,493
Derivative Liability, Current 1,697 1,738
Derivative Liability, Noncurrent 420 374
Derivative Liability, Fair Value, Gross Liability 2,117 2,112
Net derivative assets (liabilities) (107) 381
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Total derivative assets 2,010 2,493
Derivative Liability, Fair Value, Gross Liability 2,117 2,112
Interest Rate Swap [Member]    
Derivatives, Fair Value [Line Items]    
Derivative assets, current 0 0
Derivative Asset, Noncurrent 1 4
Total derivative assets 1 4
Derivative Liability, Current 37 44
Derivative Liability, Noncurrent 53 70
Derivative Liability, Fair Value, Gross Liability 90 114
Net derivative assets (liabilities) (89) (110)
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Total derivative assets 1 4
Derivative Liability, Fair Value, Gross Liability 92 112
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Total derivative assets 0 0
Derivative Liability, Fair Value, Gross Liability $ (2) $ 2