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Supplemental Oil And Gas Information (Schedule Of Changes In The Standardized Measure Of Discounted Future Net Cash Flows From Proved Oil And Gas Reserves) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Supplemental Oil And Gas Information [Abstract] |  |  |
Balance, beginning of year | $ 13,976 | $ 8,170 | $ 5,815
Sales, net of production costs and taxes | (1,646) | (2,611) | (1,239)
Discoveries and extensions, net of costs | 154 | 798 | 123
Purchase of reserves in place |  | 143 |
Sale of reserves in place | (26) |  |
Net changes in prices and production costs | (3,348) | 4,304 | 1,780
Revisions of quantity estimates | (3,058) | 2,180 | 1,611
Previously estimated development cost incurred during the year |  | 210 |
Changes in future development costs | 1,016 | 78 | (228)
Changes in timing and other | 86 | (4) | (164)
Accretion of discount | 1,211 | 708 | 472
Net change in income taxes |  |  |
Balance, end of year | $ 8,365 | $ 13,976 | $ 8,170

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- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of extensions, discoveries and improved recovery of proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Form 20-F -Section Item 18 -Subsection Instruction 2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35A -URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6807758-109447 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=34713648&loc=d3e63123-109448 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62500-109447 + Details
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