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Fair Value Measurements Proved and Unproved Oil and Gas Properties and Other Property and Equipment (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Impairment of Proved Oil and Gas Properties | $ 0 | $ 0 | $ 0 | $ 0 |
Abandonment and impairment of unproved oil and gas properties | 9,055 | $ 0 | 26,615 | 157 |
Properties held for sale, net | 5,040 |  | 5,040 |  | $ 111,700
Properties Held-for-sale, Fair Value | 5,040 |  | 5,040 |  | 0
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Properties held for sale, net | $ 5,040 |  | $ 5,040 |  | $ 111,700
Divide County Disposal Group [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  |  |  | $ 526,500 |

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- Definition The impairment expense recorded to reduce the value of proved oil and gas assets. + References No definition available. + Details
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- Definition Amount classified as property, plant and equipment attributable to disposal group held for sale or disposed of. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109222160&loc=d3e1107-107759 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=109222160&loc=SL51721533-107759 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5B -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760 + Details
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