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Accounting for Derivative Instruments and Hedging Activities - Fair value within the derivative instrument valuation (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Liabilities	$ 839	$ 977
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	958	1,081
Derivative Liabilities	839	977
Not Designated as Hedging Instrument | Interest rate contracts current
Derivative [Line Items]
Derivative Assets	15	17
Derivative Liabilities	0	0
Not Designated as Hedging Instrument | Interest rate contracts long-term
Derivative [Line Items]
Derivative Assets	14	22
Derivative Liabilities	0	0
Not Designated as Hedging Instrument | Commodity contracts current
Derivative [Line Items]
Derivative Assets	596	747
Derivative Liabilities	489	673
Not Designated as Hedging Instrument | Commodity contracts long-term
Derivative [Line Items]
Derivative Assets	333	295
Derivative Liabilities	$ 350	$ 304

X

- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
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-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

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-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
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X

- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

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-Name Accounting Standards Codification
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

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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.

+ References

No definition available.

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