Property, Plant And Equipment (Aging of Capitalized Exploratory Well Costs) (Details) (USD $)	12 Months Ended
Dec. 31, 2014 item	Dec. 31, 2013 item	Dec. 31, 2012 item	Dec. 31, 2011
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	$ 120,455,000us-gaap_CapitalizedExploratoryWellCosts	$ 393,030,000us-gaap_CapitalizedExploratoryWellCosts	$ 445,697,000us-gaap_CapitalizedExploratoryWellCosts	$ 556,412,000us-gaap_CapitalizedExploratoryWellCosts
No. of Wells	8	32	44
No. of Projects	3	9	15
Zero to one year [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount		56,499,000	59,833,000
No. of Wells		3	7
No. of Projects		1	2
One to two years [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	59,330,000	60,787,000	18,335,000
No. of Wells	3	7	2
No. of Projects	1	1	3
Two to three years [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	6,606,000		83,314,000
No. of Wells	3		9
No. of Projects			4
Three years or more [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amount	$ 54,519,000	$ 275,744,000	$ 284,215,000
No. of Wells	2	22	26
No. of Projects	2	7	6

Projects that have Exploratory Well Costs that have been Capitalized

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- Definition

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

+ Details

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- Definition

The number of productive exploratory wells drilled in the geographic area. A productive well is a well that is not a dry well. The number of wells drilled refers to the number of wells (holes) completed at any time during the fiscal years, regardless when drilling was initiated.

+ References

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

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 6

-Subparagraph A

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