Income Taxes (Income Tax Years Subject To Examination By Major Tax Jurisdictions) (Details) - Minimum [Member]	12 Months Ended
Dec. 31, 2019
United States
Income Tax Examination [Line Items]
Income tax examination year under examination	2009
Gabon [Member]
Income Tax Examination [Line Items]
Income tax examination year under examination	2015

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.

Name:	us-gaap_IncomeTaxExaminationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration