Annual report pursuant to Section 13 and 15(d)

Note 10 - Derivative Financial Instruments - Summary of Open Commodity Derivative Contracts (Details)

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Note 10 - Derivative Financial Instruments - Summary of Open Commodity Derivative Contracts (Details)
 12 Months Ended
Dec. 31, 2019
$ / shares
bbl
NYMEX Crude Oil Calls [Member] | Open Crude Oil Derivative Contracts 1 [Member] | Long [Member]  
Termination Period May 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 10,000 [1]
Notional Quantity (Bbls) 1,520,000 [1]
Strike Price (in dollars per share) $ 61
NYMEX Crude Oil Calls [Member] | Open Crude Oil Derivative Contracts 2 [Member] | Long [Member]  
Termination Period December 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 10,000 [1]
Notional Quantity (Bbls) 2,140,000 [1]
Strike Price (in dollars per share) $ 67.50
NYMEX Crude Oil Swap [Member] | Open Crude Oil Derivative Contracts 1 [Member]  
Termination Period May 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 1,500 [1]
Notional Quantity (Bbls) 228,000 [1]
Strike Price (in dollars per share) $ 60.80
NYMEX Crude Oil Swap [Member] | Open Crude Oil Derivative Contracts 2 [Member]  
Termination Period May 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 5,000 [1]
Notional Quantity (Bbls) 760,000 [1]
Strike Price (in dollars per share) $ 61
NYMEX Crude Oil Swap [Member] | Open Crude Oil Derivative Contracts 3 [Member]  
Termination Period May 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 3,500 [1]
Notional Quantity (Bbls) 532,000 [1]
Strike Price (in dollars per share) $ 60.85
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 1 [Member]  
Termination Period December 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 9,000 [1]
Notional Quantity (Bbls) 1,926,000 [1]
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 1 [Member] | Long [Member] | Put Option [Member]  
Strike Price (in dollars per share) $ 45
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 1 [Member] | Short [Member] | Call Option [Member]  
Strike Price (in dollars per share) $ 63.50
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 2 [Member]  
Termination Period December 2020
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 1,000 [1]
Notional Quantity (Bbls) 214,000 [1]
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 2 [Member] | Long [Member] | Put Option [Member]  
Strike Price (in dollars per share) $ 45
NYMEX Crude Oil Collars [Member] | Open Crude Oil Derivative Contracts 2 [Member] | Short [Member] | Call Option [Member]  
Strike Price (in dollars per share) $ 63.60
NYMEX Natural Gas Two Way Collars [Member]  
Termination Period December 2022
Notional Quantity (Bbls/day) (Barrel of Oil) | bbl 40,000 [2]
Notional Quantity (Bbls) 43,840,000 [2]
Strike Price (in dollars per share) $ 3
[1] Bbls = Barrels
[2] Bbls = Barrels