Note 5 - Derivative Financial Instruments - Commodity Derivative Contracts (Details) - Not Designated as Hedging Instrument [Member]	9 Months Ended
	Sep. 30, 2021 $ / bbl bbl
Crude Oil Derivative Swap Q4 2021 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	460.0
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	61.91
Crude Oil Derivative Swap Q1 2022 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	450.0
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	61.91
Crude Oil Derivative Swap Q2 2022 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	302.5
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	62.16
Crude Oil Derivative Swap Q3 2022 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	66.0
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	57.22
Crude Oil Derivative Swap Q4 2022 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	202.4
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	57.22
Crude Oil Derivative Swap 2022 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	1,020.9
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	60.75
Crude Oil Derivative Swap Q1 2023 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	198.0
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	57.22
Crude Oil Derivative Swap Q2 2023 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	200.2
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	57.22
Crude Oil Derivative Swap 2023 [Member]
Volume (MBbls) (Barrel of Oil) | bbl	398.2
Price per Bbl (in USD per Barrel of Oil) | $ / bbl	57.22