Derivative Instruments and Hedging Activities (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	$ 830		$ 890
Derivative Liability, Fair Value	0		0
Non-cash Portion of (Gain) Loss on Commodity Derivative Instruments	(210)us-gaap_GainLossOnSaleOfDerivatives	33us-gaap_GainLossOnSaleOfDerivatives
(Gain) Loss on Commodity Derivative Instruments	60	42
(Gain) Loss on Commodity Derivative Instruments	(150)	75
Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	661		710
Derivative Liability, Fair Value	0		0
Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	169		180
Derivative Liability, Fair Value	0		0
Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Non-cash Portion of (Gain) Loss on Commodity Derivative Instruments	(185)	27
(Gain) Loss on Commodity Derivative Instruments	55	28
(Gain) Loss on Commodity Derivative Instruments	(130)	55
Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Non-cash Portion of (Gain) Loss on Commodity Derivative Instruments	(25)	6
(Gain) Loss on Commodity Derivative Instruments	5	14
(Gain) Loss on Commodity Derivative Instruments	$ (20)	$ 20

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (e)

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- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(h))

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open derivatives, commodity, or energy contracts, held at each balance sheet date, that was included in earnings for the period.

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