Risk Management Fair Value of Derivative Contracts (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Fair value of debt, purchase accounting adjustments	$ 687	$ 638
Debt fair value adjustment, hedged instruments	212	602
Debt Instrument, Unamortized Discount	32	30
Asset derivatives	399	689
Liability derivatives	(88)	(34)
Unamortized premium	550	488
Amortization period of unamortized premium	16 years
Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	375	685
Liability derivatives	(86)	(30)
Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(39)	(33)
Balance sheet, derivative liability reduction, gross	0	0
Derivative liabilities presented on balance sheet	(39)	(33)
Derivative liability, net	(13)	(11)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(49)	(1)
Balance sheet, derivative liability reduction, gross	0	0
Derivative liabilities presented on balance sheet	(49)	(1)
Derivative liability, net	(39)	(1)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	114	82
Liability derivatives	(37)	(29)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	37	42
Liability derivatives	(21)	(18)
Commodity Contract [Member] \| Designated as Hedging Contracts [Member] \| Non-current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	77	40
Liability derivatives	(16)	(11)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	24	4
Liability derivatives	(2)	(4)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	20	4
Liability derivatives	(1)	(3)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member] \| Current-Assets held for Sale/ Accrued other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives	(1)	(1)
Commodity Contract [Member] \| Not Designated as Hedging Contracts [Member] \| Other Long-term Investments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	4	0
Interest Rate Swap [Member] \| Designated as Hedging Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	261	603
Liability derivatives	(49)	(1)
Interest Rate Swap [Member] \| Designated as Hedging Contracts [Member] \| Current-Fair value of derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	2	9
Liability derivatives	(6)	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	259	594
Liability derivatives	(43)	(1)
Not offset on balance sheet [Member] \| Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Financial instrument, liability	26	17
Derivative, Collateral, Right to Reclaim Cash	0	5
Not offset on balance sheet [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Financial instrument, liability	10	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	138	86
Balance sheet, Derivative Reduction, Gross	0	0
Derivative Assets	138	86
Derivative asset, net	111	69
Energy Related Derivative [Member] \| Not offset on balance sheet [Member]
Derivatives, Fair Value [Line Items]
Financial instrument, asset	(26)	(17)
Derivative, Collateral, Obligation to Return Cash	(1)	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	261	603
Balance sheet, Derivative Reduction, Gross	0	0
Derivative Assets	261	603
Derivative asset, net	251	603
Interest Rate Swap [Member] \| Not offset on balance sheet [Member]
Derivatives, Fair Value [Line Items]
Financial instrument, asset	(10)	0
Derivative, Collateral, Obligation to Return Cash	$ 0	$ 0

Balance sheet, derivative liability reduction, gross

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- Definition

Balance sheet, Derivative Reduction, Gross

+ References

No definition available.

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- Definition

Debt fair value adjustment, hedged instruments

+ References

No definition available.

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- Definition

Derivative asset, net

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- Definition

Derivative liabilities presented on balance sheet

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- Definition

Derivative liability, net

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No definition available.

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- Definition

Fair value of debt, purchase accounting adjustments

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No definition available.

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- Definition

Financial instrument, asset

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No definition available.

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- Definition

Financial instrument, liability

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No definition available.

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- Definition

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.

+ References

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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 FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

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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

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-Name Statement of Financial Accounting Standard (FAS)

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-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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- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

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-Paragraph 10

-Subparagraph (a)

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-Number FIN39-1

-Paragraph 10A, 10B

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-Paragraph 4, 17

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- Definition

The amount of the obligation to return cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

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- Definition

The amount of the right to reclaim cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

+ References

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- Definition

Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

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-Paragraph 205G

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-Paragraph 44C

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-Clause 1

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-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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- Definition

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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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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