Quarterly report pursuant to Section 13 or 15(d)

Acquisitions And Dispositions (Summarized Results Of Discontinued Operations) (Details)

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Acquisitions And Dispositions (Summarized Results Of Discontinued Operations) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Loss from discontinued operations $ (174) $ (15,783) $ (518) $ (7,997)
Discontinued Operations [Member] | Joint Operating With Republic Of Angola [Member]        
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]        
Exploration expense   15,269   15,270
Depreciation, depletion and amortization   3   9
General and administrative expense 174 400 512 994
Bad debt recovery and other       (7,629)
Total operating costs, expenses and (recovery) 174 15,672 512 8,644
Other operating loss, net   (7)   (28)
Operating loss (174) (15,679) (512) (8,672)
Interest income       3,201
Other, net   6 (3) 551
Total other income (expense)   6 (3) 3,752
Loss from discontinued operations before income taxes (174) (15,673) (515) (4,920)
Income tax expense   110 3 3,077
Loss from discontinued operations $ (174) $ (15,783) $ (518) $ (7,997)