Derivative Instruments (Details 2) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Derivatives recorded on BS by location [Line Items]
Current derivative assets	$ 569	$ 725
Long-term derivative assets	110	170
Total derivative assets	679	895
Current derivative liabilities	643	718
Long-term derivative liabilities	221	370
Total derivative liabilities	864	1,088
Net derivative assets (liabilities)	(185)	(193)
Derivative asset fair value	679	895
Derivative liability fair value	864	1,088
Interest Rate Swaps
Derivatives recorded on BS by location [Line Items]
Current derivative assets
Long-term derivative assets	1	4
Total derivative assets	1	4
Current derivative liabilities	195	197
Long-term derivative liabilities	119	174
Total derivative liabilities	314	371
Net derivative assets (liabilities)	(313)	(367)
Interest Rate Swaps \| Designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value		2
Derivative liability fair value	49	143
Interest Rate Swaps \| Not designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value	1	2
Derivative liability fair value	265	228
Commodity instruments
Derivatives recorded on BS by location [Line Items]
Current derivative assets	569	725
Long-term derivative assets	109	166
Total derivative assets	678	891
Current derivative liabilities	448	521
Long-term derivative liabilities	102	196
Total derivative liabilities	550	717
Net derivative assets (liabilities)	128	174
Commodity instruments \| Designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value	104	161
Derivative liability fair value	41	52
Commodity instruments \| Not designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value	574	730
Derivative liability fair value	509	665
Designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value	104	163
Derivative liability fair value	90	195
Not designated as cash flow hedge
Derivatives recorded on BS by location [Line Items]
Derivative asset fair value	575	732
Derivative liability fair value	$ 774	$ 893

Fair values as of the balance sheet date for all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments and which are expected to be converted into cash or otherwise disposed of within a year, presented gross of master netting arrangements.

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Fair values as of the balance sheet date for all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments and which are expected to be converted into cash or otherwise disposed greater than a year, presented gross of master netting arrangements.

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Fair value as of the balance sheet date of the gross assets less the gross liabilities of a derivative asset or group of derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611

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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
-Name Accounting Standards Codification
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-Publisher FASB
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-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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-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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Fair value as of the balance sheet date of the assets less the liabilities of a derivative or group of derivatives.

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Carrying amount as of the balance sheet date of the asset arising from derivative instruments and hedging activities, which are expected to be converted into cash or otherwise disposed of within a year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Carrying amount as of the balance sheet date of the assets arising from derivative contracts and hedging activities, which are expected to be converted into cash or otherwise disposed of after a year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-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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Fair value as of the balance sheet date of the gross assets less the gross liabilities of a derivative liability or group of derivative liabilities.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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