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Note 15 - Hourglass Sands (Details Textual) - USD ($) $ in Thousands | 1 Months Ended | 2 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Aug. 31, 2020 | Dec. 31, 2019 | Feb. 28, 2018 | Feb. 28, 2018 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2019
Asset Impairment Charges, Total |  |  |  |  | $ 0 | $ 1,799 | $ 0 | $ 1,799 |
Hourglass Sands [Member] |  |  |  |  |  |  |  |  |
Asset Impairment Charges, Total | $ 1,800 | $ 2,900 |  |  |  | $ 1,800 |  |  | $ 2,900
Hourglass Sands [Member] |  |  |  |  |  |  |  |  |
Capitalization, Long-term Debt and Equity, Total |  |  | $ 8,000 | $ 8,000 |  |  |  |  |
Capital Unit, Class A [Member] | Hourglass Sands [Member] |  |  |  |  |  |  |  |  |
Noncontrolling Interest, Ownership Percentage by Parent |  |  |  |  | 100.00% |  | 100.00% |  |
Percentage of Profit Until Capital Investment and Interest is Returned |  |  |  |  | 100.00% |  | 100.00% |  |
Percentage of Profit After Capital Investment and Interest is Returned |  |  |  |  | 90.00% |  | 90.00% |  |
Hourglass Sands LLC [Member] |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Total |  |  | 4,000 | $ 4,000 |  |  |  |  |
Hourglass Sands LLC [Member] | Director [Member] |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred, Total |  |  | $ 4,000 |  |  |  |  |  |

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