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Divestitures, Assets Held for Sale, and Acquisitions Acquisitions (Details) $ in Thousands | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Mar. 31, 2017 USD ($) | Jun. 30, 2017 USD ($) | Jun. 30, 2017 USD ($) a | Jun. 30, 2016 USD ($) | Jun. 30, 2017 USD ($)
Business Acquisition [Line Items] |  |  |  |  |
Payments to Acquire Oil and Gas Property and Equipment |  |  | $ 88,140 | $ 17,751 |
Other Howard and Martin Counties Trades [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Non-monetary Trade, Acreage Acquired | a |  |  | 6,550 |  |
Non-monetary Trade, Acreage Exchanged | a |  |  | 5,700 |  |
Rock Oil Acquisition 2016 [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Payments to Acquire Businesses, Gross | $ 7,400 |  |  |  | $ 998,400
Other Midland Basin Acquisition 2017 [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Net Acres Acquired | a |  |  | 3,400 |  |
Payments to Acquire Oil and Gas Property and Equipment |  |  | $ 72,300 |  |
QStar Acquisition 2016 [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Payments to Acquire Oil and Gas Property and Equipment |  |  | $ 7,100 |  |
Acquisition of Oil And Gas Property And Equipment, Consideration Transferred |  | $ 1,600,000 |  |  |

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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585 + Details
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