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Divestitures, Assets Held for Sale, and Acquisitions Acquisitions (Details) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 USD ($) a | Jun. 30, 2018 USD ($) a | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) a
Business Acquisition [Line Items] |  |  |  |
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) |  |  | $ 95,121 |
Payments to Acquire Oil and Gas Property and Equipment |  |  | $ 24,571 | $ 87,389
Howard and Martin Counties Trades 2018 [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Non-monetary Trade, Acreage Acquired | a | 2,658 |  |  |
Non-monetary Trade, Acreage Exchanged | a | 2,654 |  |  |
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) | $ 95,100 |  |  |
Gain or loss recognized on trade | $ 0 |  |  |
Howard and Martin Counties Trades 2017 [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Non-monetary Trade, Acreage Acquired | a |  |  |  | 7,425
Non-monetary Trade, Acreage Exchanged | a |  |  |  | 6,725
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) |  |  |  | $ 283,700
Gain or loss recognized on trade |  |  |  | $ 0
Other Martin County Acquisition 2018 [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Net Acres Acquired | a |  | 720 |  |
Payments to Acquire Oil and Gas Property and Equipment |  | $ 24,600 |  |
Other Howard and Martin Counties Acquisitions 2017 [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Net Acres Acquired | a |  |  |  | 3,400
Payments to Acquire Oil and Gas Property and Equipment |  |  |  | $ 72,200

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- Definition The net book value of a nonmonetary asset transferred or exchanged in connection with the acquisition of a business or asset in a noncash transaction. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Nonmonetary assets and liabilities are assets and liabilities that will not result in cash receipts or cash payments in the future. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586 + Details
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