Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands, in Billions					1 Months Ended	6 Months Ended	12 Months Ended
	May 06, 2019 $ / bbl bbl	Sep. 26, 2018 USD ($)	Sep. 17, 2018 USD ($)	Sep. 17, 2018 XAF ( )	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) bbl	Dec. 31, 2018 USD ($) $ / bbl	Dec. 31, 2017 USD ($)	Dec. 31, 2019 XAF ( ) / $
Organization And Accounting Policies [Line Items]
Reduction in VAT receivable							$ 275	$ (777)	$ (3,025)
Exchange rate | / $										585.7
Bad debt recovery (expense)							341	77	(452)
Inventory adjustment							0		0
Interest Costs Capitalized							0	0	0
Asset retirement obligation, revision of estimate					$ (400)		$ (379)	$ (6,527)	703
Monthly royalty rate, based on production at the published price							13.00%
Working interest of carried partner, percentage							7.50%
Future working interest of carried partner percentage							10.00%
Derivative cap price | $ / bbl								74.00
Derivative floor price | $ / bbl								74.00
Gain (loss) on foreign currency transactions							$ (200)	$ (100)	500
Barrels | bbl							274,870
Cash received to settle derivatives							$ 2,400	700	200
Restatement Adjustment [Member]
Organization And Accounting Policies [Line Items]
Accrued liabilities									(2,600)
Office Equipment [Member]
Organization And Accounting Policies [Line Items]
Estimated useful life							5 years
Leasehold Improvements [Member] | Minimum [Member]
Organization And Accounting Policies [Line Items]
Estimated useful life							5 years
Leasehold Improvements [Member] | Maximum [Member]
Organization And Accounting Policies [Line Items]
Estimated useful life							7 years
Gabon [Member]
Organization And Accounting Policies [Line Items]
Receivable balance, gross |										5.4
Receivable balance, net, noncurrent |										1.8
Reduction in VAT receivable, gross amount		$ 25,000		14.1
Reduction in VAT receivable		$ 8,400	$ 4,200	4.7
Bad debt recovery (expense)							$ 300	100	$ (400)
Inventory adjustment								400
Asset retirement obligation, revision of estimate						$ 400
Etame Field [Member]
Organization And Accounting Policies [Line Items]
Asset retirement obligation, revision of estimate						$ 600		$ (6,500)
Commodity Contract, July 19 Through June 2020 [Member]
Organization And Accounting Policies [Line Items]
Derivative, average price per barrel | $ / bbl	66.70
Barrels | bbl	500,000