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Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands | 9 Months Ended |
--- | --- | ---
Sep. 30, 2023 | Dec. 31, 2022
Investment Plan, Maximum Amount. Approved |  | $ 20,000
Inventory, Net | $ 325 | 392
Equipment Contstructed for Resale [Member] |  |
Inventory, Net | 207 | 207
Spare Parts [Member] |  |
Inventory, Net | 118 | 185
In Process Equipment [Member] |  |
Inventory, Net | $ 619 | $ 634
Minimum [Member] |  |
Debt Securities, Held-to-maturity, Maturity Term (Month) | 3 months |
Maximum [Member] |  |
Debt Securities, Held-to-maturity, Maturity Term (Month) | 36 months |
Asset Pledged as Collateral [Member] | Letter of Credit [Member] |  |
Restricted Cash and Investments | $ 1,488 |
Asset Pledged as Collateral [Member] | Letter of Credit [Member] | Varying Maturity Dates Expiring No Later Than September 30, 2024 [Member] |  |
Restricted Cash and Investments | 1,197 |
Asset Pledged as Collateral [Member] | Letter of Credit [Member] | Latest Maturity Date No Later Than November 30, 2025 [Member] |  |
Restricted Cash and Investments | $ 291 |

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