Note 9 - Derivative Financial Instruments - Cash Receipts on Commodity Derivative Contract Settlements (Details) - USD ($) $ in Thousands  | 
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020  | 
Dec. 31, 2019  | 
Dec. 31, 2018  | 
|
| Derivatives cash receipts (payments), net | $ 45,196 | $ 13,941 | $ (28,164) | 
| X | ||||||||||
- Definition The cash inflow (outflow) from derivative instruments during the period, which are classified as operating activities, excluding those designated as hedging instruments. No definition available. 
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