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Fair Value Measurements - Hierarchy of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Assets: |  |
Total assets | $ 142 | $ 495
Liabilities: |  |
Total liabilities | 169,356 | 135,567
Money market funds [Member] |  |
Assets: |  |
Total assets | 142 | 142
Commodity derivative instruments [Member] |  |
Assets: |  |
Total assets |  | 353
Liabilities: |  |
Total liabilities | 169,356 | 135,567
Level 1 [Member] |  |
Assets: |  |
Total assets | 142 | 142
Liabilities: |  |
Total liabilities | 0 | 0
Level 1 [Member] | Money market funds [Member] |  |
Assets: |  |
Total assets | 142 | 142
Level 1 [Member] | Commodity derivative instruments [Member] |  |
Assets: |  |
Total assets |  | 0
Liabilities: |  |
Total liabilities | 0 | 0
Level 2 [Member] |  |
Assets: |  |
Total assets | 0 | 353
Liabilities: |  |
Total liabilities | 169,356 | 135,567
Level 2 [Member] | Money market funds [Member] |  |
Assets: |  |
Total assets | 0 | 0
Level 2 [Member] | Commodity derivative instruments [Member] |  |
Assets: |  |
Total assets |  | 353
Liabilities: |  |
Total liabilities | 169,356 | 135,567
Level 3 [Member] |  |
Assets: |  |
Total assets | 0 | 0
Liabilities: |  |
Total liabilities | 0 | 0
Level 3 [Member] | Money market funds [Member] |  |
Assets: |  |
Total assets | 0 | 0
Level 3 [Member] | Commodity derivative instruments [Member] |  |
Assets: |  |
Total assets |  | 0
Liabilities: |  |
Total liabilities | $ 0 | $ 0

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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