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Fair Value Measurements (Details) - USD ($) shares in Millions |  | 12 Months Ended
--- | --- | ---
Dec. 21, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Financial assets and liabilities measured at fair value on a recurring basis |  |  |  |  |  |  |
Impairment of Long-Lived Assets Held-for-use |  |  | $ 0 |  | $ 0 |  | $ 49,369,000
Impairment of Proved Oil and Gas Properties |  |  | 3,806,000 |  | 354,614,000 |  | $ 468,679,000
Assets: |  |  |  |  |  |  |
Derivatives |  |  | 104,628,000 |  | 122,096,000 |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  |  | 243,984,000 |  | 213,804,000 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Derivatives | [1] |  | 0 |  |  |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability | [1] |  | 0 |  |  |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Derivatives | [1] |  | 0 |  |  |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability | [1] |  | 0 |  |  |  |
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Total property and equipment, net | [2] |  |  |  | 0 |  |
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Total property and equipment, net | [2] |  |  |  | 0 |  |
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Total property and equipment, net | [2] |  |  |  | 88,205,000 |  |
Disposal group, held-for-sale, not discontinued operations [Member] | Divide County disposal group [Member] |  |  |  |  |  |  |
Financial assets and liabilities measured at fair value on a recurring basis |  |  |  |  |  |  |
Impairment of Proved Oil and Gas Properties |  |  | 526,500,000 |  |  |  |
QStar Acquisition 2016 [Member] |  |  |  |  |  |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Private issuance of Common Stock for an acquisition |  | 13.4 |  |  |  |  |
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Derivatives | [3] |  |  |  | 0 |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability | [3] |  |  |  | 0 |  |
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Derivatives |  |  | 104,628,000 | [1] | 122,096,000 | [3] |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability |  |  | $ 243,984,000 | [1] | 213,804,000 | [3] |
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |
Derivatives | [3] |  |  |  | 0 |  |
Liabilities [Abstract] |  |  |  |  |  |  |
Derivative Liability, Fair Value, Gross Liability | [3] |  |  |  | $ 0 |  |
[1] | This represents a financial asset or liability that is measured at fair value on a recurring basis.
[2] | This represents a non-financial asset that is measured at fair value on a nonrecurring basis.
[3] | This represents a financial asset or liability that is measured at fair value on a recurring basis.

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