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Supplemental Oil And Gas Information (Schedule Of Net Proved Oil And Gas Reserves And The Changes In Net Proved Oil And Gas Reserves) (Details) | 12 Months Ended
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Dec. 31, 2017 MBoe MMcf MBbls | Dec. 31, 2016 MBoe MMcf MBbls | Dec. 31, 2015 MBoe MMcf MBbls | Dec. 31, 2014 MBoe MMcf MBbls
Reserve Quantities [Line Items] |  |  |  |
Proved reserves | 730 | 877 | 1,797 |
Revisions of previous estimates | 195 | (36) | (790) |
Improved recovery |  |  |  |
Purchase of reserves in place |  |  |  |
Extensions and discoveries | 47 | 3 | 1 |
Production | (102) | (108) | (131) |
Sales of reserves in place |  | (6) |  |
Proved reserves | 870 | 730 | 877 | 1,797
Proved developed reserves (equivalent) | MBoe | 832 | 730 | 877 | 1,438
Proved undeveloped reserves (equivalent) | MBoe | 38 |  |  | 359
Oil [Member] |  |  |  |
Reserve Quantities [Line Items] |  |  |  |
Proved reserves | 730 | 877 | 1,797 |
Revisions of previous estimates | 195 | (36) | (790) |
Improved recovery |  |  |  |
Purchase of reserves in place |  |  |  |
Extensions and discoveries | 47 | 3 | 1 |
Production | (102) | (108) | (131) |
Sales of reserves in place |  | (6) |  |
Proved reserves | 870 | 730 | 877 | 1,797
Proved developed reserves (volume) | 832 | 730 | 877 | 1,438
Proved undeveloped reserves (volume) | 38 |  |  | 359
Gas [Member] |  |  |  |
Reserve Quantities [Line Items] |  |  |  |
Proved reserves | MMcf |  |  |  |
Revisions of previous estimates | MMcf |  |  |  |
Improved recovery | MMcf |  |  |  |
Purchase of reserves in place | MMcf |  |  |  |
Extensions and discoveries | MMcf |  |  |  |
Production | MMcf |  |  |  |
Sales of reserves in place | MMcf |  |  |  |
Proved reserves | MMcf |  |  |  |
Proved developed reserves (volume) | MMcf |  |  |  |
Proved undeveloped reserves (volume) | MMcf |  |  |  |

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- Definition Energy measure of interests in proved developed reserves of crude oil, including condensate and natural gas liquids, natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas. + References No definition available. + Details
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- Definition Energy measure of proved undeveloped reserves of crude oil, including condensate and natural gas liquids, natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas. + References No definition available. + Details
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- Definition Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Changes in proved reserve estimates resulting from application of improved recovery techniques. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-10.(a)(2)) -URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e511914-122862 + Details
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- Definition Production of proved reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61884-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61797-109447 + Details
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