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
Mar. 31, 2017
Mar. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Income (loss) from discontinued operations $ (176) $ 7,806
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]    
General and administrative expense 171 298
Bad debt expense (recovery) and other   (7,625)
Total operating costs and expenses 171 (7,327)
Other operating loss, net   (21)
Operating income (loss) (171) 7,306
Interest income   3,201
Other, net (2) 266
Total other income (2) 3,467
Income (loss) from discontinued operations before income taxes (173) 10,773
Income tax expense 3 2,967
Income (loss) from discontinued operations $ (176) $ 7,806