Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015 pit
Crude Oil and Natural Gas
Long-term Purchase Commitment [Line Items]
Delivery commitments (MMBOE)	5,500
Mitchell County, Texas
Long-term Purchase Commitment [Line Items]
Number of sites	9
Anticipated cost of cleanup, remediation and related costs	$ 2.5
Costs incurred for cleanup, remediation and related items	$ 1.9

Environmental Exit Costs, Number of Sites

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- Definition

Oil And Gas Delivery Commitments And Contracts, Remaining Contractual Amount (BOE)

+ References

No definition available.

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- Definition

The aggregate amount disbursed during the reporting period to settle environmental loss contingencies.

+ References

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- Definition

Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q4)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 4

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