Supplemental Gas Data Oil and Gas Expenditures (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Proven properties	$ 0	$ 0	$ 50,005
Unproven properties	119,597	260,477	28,634
Development	952,733us-gaap_CostsIncurredDevelopmentCosts	629,100us-gaap_CostsIncurredDevelopmentCosts	339,608us-gaap_CostsIncurredDevelopmentCosts
Exploration	45,006us-gaap_CostsIncurredExplorationCosts	95,413us-gaap_CostsIncurredExplorationCosts	130,312us-gaap_CostsIncurredExplorationCosts
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities	$ 1,117,336	$ 984,990	$ 548,559

Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have proved reserves.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

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-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62038-109447

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Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have unproved reserves.

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Development costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities.

+ References

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

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Exploration costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Exploration

-URI http://asc.fasb.org/extlink&oid=6512329

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Amount of costs incurred related to oil and gas property acquisition, exploration and development activities, including capitalized costs and costs charged to expense.

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