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. No definition available.
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- Definition Tax year being audited in the income tax examination, in CCYY format. No definition available.
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