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Crude Oil and Natural Gas Properties and Equipment (Narrative) (Details) |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 20, 2026 | Sep. 26, 2018 USD ($) | Sep. 17, 2018 USD ($) item | Feb. 29, 2020 USD ($) | Sep. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Sep. 30, 2020 USD ($) item | Sep. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 | Dec. 31, 2012
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Reduction in VAT receivable |  |  |  |  |  |  | $ (919,000) | $ 664,000 |  |  |
Impairment of proved crude oil and natural gas properties |  |  |  |  | $ 0 |  | 30,625,000 |  |  |  |
Property, net |  |  |  |  | 38,845,000 |  | 38,845,000 |  | $ 68,258,000 |  |
Etame Marine Block [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allocated to proved leasehold cost |  |  |  |  | 2,300,000 |  | 2,300,000 |  |  |  |
Impairment of proved crude oil and natural gas properties |  |  |  |  |  | $ 30,600,000 |  |  |  |  |
Property, net |  |  |  |  |  | $ 15,600,000 |  |  |  |  |
Undeveloped leasehold value |  |  |  |  | $ 11,500,000 |  | $ 11,500,000 |  |  |  |
Etame Marine Block [Member] | VAALCO Gabon S.A. [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage |  |  |  |  | 33.575% |  | 33.575% |  |  |  |
Block P Offshore Equatorial Guinea [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage |  |  |  |  | 43.00% |  | 43.00% |  |  |  | 31.00%
Increase (decrease) in working interest ownership percentage |  |  |  |  |  |  | 12.00% |  |  |  |
Undeveloped acreage |  |  |  |  | $ 10,000,000.0 |  | $ 10,000,000.0 |  |  |  |
Potential payment |  |  |  |  | $ 3,100,000 |  | $ 3,100,000 |  |  |  |
Period of development |  |  |  |  |  |  | 25 years |  |  |  |
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Consortium [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Entitled percent for consortium after initial royalty percentage |  |  |  |  |  |  | 70.00% |  |  |  |
Monthly royalty rate, based on production at the published price |  |  |  |  |  |  | 13.00% |  |  |  |
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Government Of Gabon [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Monthly royalty rate, based on production at the published price |  |  |  |  |  |  | 13.00% |  |  |  |
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Etame Marine Block [Member] | Consortium [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage |  |  |  |  | 7.50% |  | 7.50% |  |  |  |
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Etame Marine Block [Member] | Government Of Gabon [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage |  |  |  |  |  |  |  |  |  | 7.50% |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Deferred tax assets, basis difference in fixed assets |  |  |  |  | $ 18,600,000 |  | $ 18,600,000 |  |  |  |
Deferred tax liabilities, basis difference in fixed assets |  |  |  |  | 18,600,000 |  | 18,600,000 |  |  |  |
Allocated to proved leasehold cost |  |  |  |  | 22,500,000 |  | 22,500,000 |  |  |  |
Allocated to unproved leasehold cost |  |  |  |  | 13,700,000 |  | 13,700,000 |  |  |  |
Estimated costs of technical studies |  |  |  |  |  |  | $ 500,000 |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Consortium [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of drilled wells required by agreement | item |  |  |  |  |  |  | 2 |  |  |  |
Number of appraisal wellbores required by agreement | item |  |  |  |  |  |  | 2 |  |  |  |
Number of wells drilled | item |  |  |  |  |  |  | 2 |  |  |  |
Number of wellbores drilled | item |  |  |  |  |  |  | 2 |  |  |  |
Number of technical studies required | item |  |  |  |  |  |  | 2 |  |  |  |
Estimated costs of technical studies |  |  |  |  |  |  | $ 1,500,000 |  |  |  |
Entitled percent for consortium after initial royalty percentage |  |  |  |  |  |  | 80.00% |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Government Of Gabon [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Monthly royalty rate, based on production at the published price |  |  |  |  |  |  | 13.00% |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Signing Bonus [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Contractual obligation |  |  | $ 21,800,000 |  |  |  |  |  |  |  |
Payment of signing bonus, allocated to proved and unproved property |  | $ 11,800,000 |  |  |  |  |  |  |  |  |
Reduction in VAT receivable |  | 8,400,000 |  | $ 4,200,000 |  |  |  |  |  |  |
Other accrued liabilities |  | 1,700,000 |  |  |  |  |  |  | $ 1,700,000 |  |
Allocated to unproved leasehold cost |  |  |  |  | 6,700,000 |  | $ 6,700,000 |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Signing Bonus [Member] | Consortium [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Contractual obligation |  |  | $ 65,000,000.0 |  |  |  |  |  |  |  |
Payment of signing bonus, allocated to proved and unproved property |  | 35,000,000.0 |  |  |  |  |  |  |  |  |
Reduction in VAT receivable |  | 25,000,000.0 |  |  |  |  |  |  |  |  |
Other accrued liabilities |  | $ 5,000,000.0 |  |  |  |  |  |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Tax Impact [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allocated to unproved leasehold cost |  |  |  |  | $ 7,100,000 |  | $ 7,100,000 |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Etame Marine Block [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of exploitation areas | item |  |  | 3 |  |  |  |  |  |  |  |
Period of agreement for exploitation areas |  |  | 10 years |  |  |  | 10 years |  |  |  |
Number of contract extension periods | item |  |  | 2 |  |  |  |  |  |  |  |
Production license agreement term extended by government |  |  | 5 years |  |  |  |  |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Etame Marine Block [Member] | Government Of Gabon [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage |  |  |  |  | 7.50% |  | 7.50% |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Scenario, Forecast [Member] | Etame Marine Block [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in working interest ownership percentage | (0.80%) |  |  |  |  |  |  |  |  |  |
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Scenario, Forecast [Member] | Etame Marine Block [Member] | Government Of Gabon [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Working interest ownership, percentage | 10.00% |  |  |  |  |  |  |  |  |  |
Increase (decrease) in working interest ownership percentage | 2.50% |  |  |  |  |  |  |  |  |  |
Production Sharing Contract, After September 16, 2028 [Member] | Consortium [Member] |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Entitled percent for consortium after initial royalty percentage |  |  |  |  |  |  | 70.00% |  |  |  |

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