Selected Quarterly Financial Information (Summary of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Selected Quarterly Financial Information [Abstract] | |||||||||||
| Revenues-oil and natural gas sales | $ 27,606 | $ 25,266 | $ 24,426 | $ 27,645 | $ 17,156 | $ 18,178 | $ 20,425 | $ 21,266 | $ 104,943 | $ 77,025 | $ 59,784 |
| Total operating costs and expenses | 12,433 | 7,940 | 19,017 | 14,631 | 14,413 | 14,454 | 15,068 | 13,055 | 54,021 | 56,990 | 63,909 |
| Operating income (loss) | 15,206 | 17,320 | 5,723 | 13,038 | 2,495 | 3,721 | 5,587 | 8,148 | 51,287 | 19,951 | (4,391) |
| Income (loss) from continuing operations | 10,504 | 78,626 | 887 | 8,711 | 3,534 | (148) | 2,451 | 4,435 | 98,728 | 10,272 | (18,267) |
| Loss from discontinued operations | (80) | (21) | (343) | (52) | (103) | (174) | (168) | (176) | (496) | (621) | (8,283) |
| Net income (loss) | $ 10,424 | $ 78,605 | $ 544 | $ 8,659 | $ 3,431 | $ (322) | $ 2,283 | $ 4,259 | $ 98,232 | $ 9,651 | $ (26,550) |
| Basic net income (loss) per share | $ 0.17 | $ 1.31 | $ 0.02 | $ 0.15 | $ 0.060 | $ 0.000 | $ 0.040 | $ 0.070 | $ 1.64 | $ 0.16 | $ (0.45) |
| Diluted net income (loss) per share | 0.17 | 1.28 | 0.02 | 0.15 | 0.060 | 0.000 | 0.040 | 0.070 | 1.62 | 0.16 | (0.45) |
| Basic income (loss) from continuing operations per share | 0.17 | 1.31 | 0.02 | 0.15 | 0.06 | 0.00 | 0.04 | 0.07 | 1.65 | 0.17 | (0.31) |
| Diluted income (loss) from continuing operations per share | $ 0.17 | $ 1.28 | $ 0.02 | $ 0.15 | $ 0.06 | $ 0.00 | $ 0.04 | $ 0.07 | $ 1.63 | $ 0.17 | $ (0.31) |
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- Definition Total costs of sales and operating expenses for the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount after tax of income (loss) from a discontinued operation including the portion attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The net result for the period of deducting operating expenses from operating revenues. No definition available.
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- References No definition available.
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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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