Annual report pursuant to Section 13 and 15(d)

Note 19 - Supplemental Oil and Gas Disclosures - Unaudited (Details Textual)

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Note 19 - Supplemental Oil and Gas Disclosures - Unaudited (Details Textual)
$ in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
MMBoe
Dec. 31, 2019
USD ($)
MMBoe
Dec. 31, 2018
USD ($)
MMBoe
Asset Retirement Obligation, Period Increase (Decrease) Due To Acquisitions Incurred and Revisions | $ $ 15.2 $ 37.5 $ 20.3
Seismic Costs | $ 0.3 7.8 1.5
Geological and Geophysical Costs | $ $ 4.5 $ 5.7 $ 5.4
Percentage of Non-operated Proved Developed Non-producing Reserves 22.10%    
Proved Undeveloped Reserve Net Energy Converted Outside of Five Years (Millions of Barrels of Oil Equivalent) 2.3    
Percentage of Proved Undeveloped Reserves Expected To Be Developed 19.00%    
Present Value Discounted Percentage. 10.00%    
Barrel Equivalent [Member] | Proved Undeveloped Reserves [Member]      
Proved Developed and Undeveloped Reserve, Net (Energy), Ending Balance (Millions of Barrels of Oil Equivalent) 12.2    
Changes Due To Price [Member]      
Proved Developed and Undeveloped Reserve, Revision of Previous Estimate (Energy) (Millions of Barrels of Oil Equivalent) 27.7   2.3
Proved Developed and Undeveloped Reserve, Extension and Discovery (Energy) (Millions of Barrels of Oil Equivalent)   10.0  
Changes at the Viosca Knoll 823 [Member]      
Proved Developed and Undeveloped Reserve, Extension and Discovery (Energy) (Millions of Barrels of Oil Equivalent)     1.3
Ewing Bank 910 Field [Member]      
Proved Developed and Undeveloped Reserve, Extension and Discovery (Energy) (Millions of Barrels of Oil Equivalent)     0.7
Mississippi Canyon 800 (Gladden) Field [Member]      
Proved Developed and Undeveloped Reserve, Extension and Discovery (Energy) (Millions of Barrels of Oil Equivalent)   0.9  
Mobile Bay and Fairway Properties [Member]      
Proved Developed and Undeveloped Reserve, Revision of Previous Estimate (Energy) (Millions of Barrels of Oil Equivalent) 26.2    
Mississippi Canyon 243 Field [Member]      
Wells Expected To Be Drilled, Year 2022    
Virgo Deepwater Fields [Member]      
Wells Expected To Be Drilled, Year 2024