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Assets Held for Sale (Details) (USD $) | 9 Months Ended |  |  |  | 9 Months Ended | 3 Months Ended
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013 | Sep. 24, 2014 Gooseneck Prospect Acquisition [Member] | Sep. 24, 2014 Gooseneck Prospect Acquisition [Member] Fair Value, Measurements, Nonrecurring [Member] | Oct. 15, 2014 Gooseneck Prospect Acquisition [Member] Subsequent Event [Member] | Sep. 30, 2014 Rocky Mountain [Member] | Jun. 30, 2014 Rocky Mountain [Member]
Business Acquisition [Line Items] |  |  |  |  |  |  |  |
Net acres acquired |  |  |  | 61,000 |  |  |  |
Cash Consideration to Acquire Proved and Unproved Property |  |  |  | $ 325,230,000 |  | $ 84,800,000 |  |
Proved Oil and Gas Property, Successful Effort Method | 6,789,927,000 |  | 5,637,462,000 |  | 201,842,000 |  |  |
Unproved Oil and Gas Property, Successful Effort Method | 536,100,000 |  | 271,100,000 |  | 125,562,000 |  |  |
Oil and Gas Property, Successful Effort Method, Net |  |  |  |  | 327,404,000 |  |  |
Working Capital Acquired |  |  |  |  | (61,000) |  |  |
Asset Retirement Obligations, Noncurrent | 123,905,000 |  | 115,659,000 |  | (2,113,000) |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net |  |  |  |  | 325,230,000 |  |  |
Leasehold Acres Consideration to Acquire Unproved Property |  |  |  |  |  |  | 7,000 |
Payments to Acquire Oil and Gas Property |  |  |  |  |  |  | 134,100,000 |
Proceeds from Sale of Oil and Gas Property and Equipment | 41,868,000 | 20,498,000 |  |  |  |  |  | 50,200,000
Gain (Loss) on Disposition of Oil and Gas Property |  |  |  |  |  |  |  | 26,800,000
Assets Held-for-sale Reasonably Certain Period for Sale | 1 |  |  |  |  |  |  |
Disposal Group, Including Discontinued Operation, Long Lived Assets, Current | 19,900,000 |  |  |  |  |  |  |
Asset retirement obligation associated with oil and gas properties held for sale | $ 452,000 |  | $ 3,033,000 |  |  |  |  |

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- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation for an asset held for sale. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References No definition available. + Details
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- Definition Represents the period where there is reasonable certainty that the sale will take place for the assets to be classified as held for sale. + References No definition available. + Details
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- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
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