Properties and Equipment (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net changes in capitalized exploratory well costs
Balance at beginning of period	$ 0us-gaap_CapitalizedExploratoryWellCosts	$ 10,390us-gaap_CapitalizedExploratoryWellCosts	$ 5,328us-gaap_CapitalizedExploratoryWellCosts
Additions to capitalized exploratory well costs pending the determination of proved reserves	10,557	0	10,390
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	0	(10,198)	0
Capitalized exploratory well costs charged to expense	0	(192)	(5,328)
Balance at end of period	$ 10,557us-gaap_CapitalizedExploratoryWellCosts	$ 0us-gaap_CapitalizedExploratoryWellCosts	$ 10,390us-gaap_CapitalizedExploratoryWellCosts

Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves.

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)(1)

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

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Capitalized exploratory well costs that were expensed during the year because proved reserves were not found at the exploratory well.

+ 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)(3)

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

+ Details

Name:	us-gaap_CapitalizedExploratoryWellCostChargedToExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

Name:	us-gaap_CapitalizedExploratoryWellCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_IncreaseDecreaseInCapitalizedExploratoryWellCostsThatArePendingDeterminationOfProvedReservesRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Previously capitalized costs of the drilling of wells that were reclassified as part of the costs of the enterprise's wells and related equipment and facilities at the time that proved reserves were found.

+ 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)(2)

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

+ Details

Name:	us-gaap_ReclassificationToWellFacilitiesAndEquipmentBasedOnDeterminationOfProvedReserves
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration