Risk Management Fair Value of Derivative Contracts (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Debt Instrument, Unamortized Premium	$ 378
Debt Instrument, Unamortized Discount		24
Asset derivatives	765	704
Liability derivatives	(56)	(160)
Unamortized premium	500	483
Amortization period of unamortized premium	18 years
Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	763	701
Liability derivatives	(54)	(155)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	111	105
Liability derivatives	(54)	(155)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	58	66
Liability derivatives	(39)	(116)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member] \| Current-Assets held for Sale/ Accrued other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	1	0
Liability derivatives	0	0
Commodity Contract [Member] \| Designated as Hedging Contracts [Member] \| Non-current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	52	39
Liability derivatives	(15)	(39)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	2	3
Liability derivatives	(2)	(5)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	1	3
Liability derivatives	(2)	(5)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member] \| Other Long-term Investments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	1	0
Interest Rate Swap [Member] \| Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	652	596
Liability derivatives	0	0
Interest Rate Swap [Member] \| Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	0	3
Liability derivatives	0	0
Interest Rate Swap [Member] \| Designated as Hedging Contracts [Member] \| Non-current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	652	593
Liability derivatives	$ 0	$ 0

Period when adjustments to the carrying value of an interest-bearing hedged item are amortized upon discontinuation of the interest rate fair value hedge, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

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-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 31

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Accounting Standards Codification

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- Definition

The amount of debt premium that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

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- Definition

Amount as of the balance sheet date of the unamortized adjustment to the carrying value of an interest-bearing hedged item made under an effective interest rate fair value hedge that is amortized upon discontinuation of the interest rate fair value hedge.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 35

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=6439857&loc=d3e75592-113984

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 24

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- Definition

Fair value of the gross assets less the gross liabilities of a derivative asset or group of derivative assets.

+ References

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-Name Accounting Standards Codification

-Topic 815

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- Definition

Fair value of the gross liabilities less the gross assets of a derivative liability or group of derivative liabilities.

+ References

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