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Income Taxes (Income Tax Years Subject To Examination By Major Tax Jurisdictions) (Details) | 12 Months Ended
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Dec. 31, 2017
U.S. [Member] | Minimum [Member] |
Income Tax Examination [Line Items] |
Income tax examination year under examination | 2008
U.S. [Member] | Maximum [Member] |
Income Tax Examination [Line Items] |
Income tax examination year under examination | 2017
Gabon [Member] | Minimum [Member] |
Income Tax Examination [Line Items] |
Income tax examination year under examination | 2013
Gabon [Member] | Maximum [Member] |
Income Tax Examination [Line Items] |
Income tax examination year under examination | 2017

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Tax year being audited in the income tax examination, in CCYY format. + References No definition available. + Details
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Balance Type: | na
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- Details
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- Details
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- Details
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- Details
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