General Information (Unaudited) (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2016 USD ($) $ / bbl	Mar. 31, 2015 USD ($)	Dec. 31, 2015 $ / bbl
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Fair Value Inputs, Discount Rate	10.00%
Accumulated Costs Related to Unproved Properties Transferred to Full Cost Pool	$ 3,100
Impairment of oil and gas properties	$ (3,787)	$ (3,104)
Crude Oil [Member]
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Average Sales Prices \| $ / bbl	46.26		50.28

The accumulated costs related to unproved properties transferred to the full cost pool.

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- Definition

The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1204
-Paragraph (b)
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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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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
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The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 35
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=28370743&loc=d3e66150-109466

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-Name Accounting Standards Codification
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-Section 45
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