Derivative Instruments (Details 2) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative assets, current	$ 959	$ 1,698
Long-term derivative assets	323	313
Total derivative assets	1,282	2,011
Derivative liabilities, current	991	1,734
Long-term derivative liabilities	436	473
Total derivative liabilities	1,427	2,207
Derivative, Fair Value, Net	(145)	(196)
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative assets	8	1
Total derivative liabilities	81	90
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative assets	1,274	2,010
Total derivative liabilities	1,346	2,117
Interest Rate Hedging Instruments
Derivatives, Fair Value [Line Items]
Derivative assets, current	0	0
Derivative Assets, Noncurrent	8	1
Total derivative assets	8	1
Current derivative liabilities	33	37
Derivative Liabilities, Noncurrent	48	53
Total derivative liabilities	81	90
Derivative, Fair Value, Net	(73)	(89)
Interest Rate Hedging Instruments | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative assets	8	1
Total derivative liabilities	81	90
Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, current	959	1,698
Derivative Assets, Noncurrent	315	312
Total derivative assets	1,274	2,010
Current derivative liabilities	958	1,697
Derivative Liabilities, Noncurrent	388	420
Total derivative liabilities	1,346	2,117
Derivative, Fair Value, Net	(72)	(107)
Energy Related Derivative [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative assets	1,274	2,010
Total derivative liabilities	$ 1,346	$ 2,117