Derivative and Hedging Activities - Derivative Instruments in Balance Sheet Table (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	$ (797)	$ (649)
Short-term derivative assets	1	0
Long-term derivative assets	7	4
Derivative Liability, Current	(417)	(208)
Long-term derivative liabilities	(389)	(445)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	(755)	(553)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	(48)	(98)
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value Gross	6	2
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	56	29
Other Noncurrent Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	3	11
Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(469)	(231)
Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(1)	(6)
Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(345)	(362)
Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, gross liability	(47)	(92)
Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6	2
Netting [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Netting [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0
Netting [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Netting [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Netting [Member] | Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	55	29
Netting [Member] | Other Noncurrent Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	3	9
Netting [Member] | Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(55)	(29)
Netting [Member] | Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Netting [Member] | Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(3)	(9)
Netting [Member] | Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Netting [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Estimate of Fair Value Measurement [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	(797)	(649)
Estimate of Fair Value Measurement [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	(755)	(553)
Estimate of Fair Value Measurement [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	(48)	(98)
Estimate of Fair Value Measurement [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	6	2
Estimate of Fair Value Measurement [Member] | Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Short-term derivative assets	1	0
Estimate of Fair Value Measurement [Member] | Other Noncurrent Assets [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Long-term derivative assets	0	2
Estimate of Fair Value Measurement [Member] | Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(414)	(202)
Estimate of Fair Value Measurement [Member] | Other Current Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(1)	(6)
Estimate of Fair Value Measurement [Member] | Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Long-term derivative liabilities	(342)	(353)
Estimate of Fair Value Measurement [Member] | Other Noncurrent Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Long-term derivative liabilities	(47)	(92)
Estimate of Fair Value Measurement [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Long-term derivative assets	$ 6	$ 2