Quarterly report pursuant to Section 13 or 15(d)

Acquisitions And Dispositions (Assets And Liabilities Attributable To Discontinued Operations) (Details)

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Acquisitions And Dispositions (Assets And Liabilities Attributable To Discontinued Operations) (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Total current assets $ 3,030 $ 2,836
Total current liabilities 15,002 15,347
Joint Operating With Republic Of Angola [Member] | Discontinued Operations [Member]    
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Accounts with partners 3,030 2,836
Total current assets 3,030 2,836
Total assets 3,030 2,836
Accounts payable 1 158
Accrued liabilities and other 15,001 15,189
Total current liabilities 15,002 15,347
Total liabilities $ 15,002 $ 15,347