Note 12 - Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2023 |
Mar. 31, 2022 |
|
| Stock-based compensation expense | $ 687 | $ 605 |
| Plant Operation and Clean Up [Member] | ||
| Stock-based compensation expense | 29 | 25 |
| Research and Development Expense [Member] | ||
| Stock-based compensation expense | 18 | 18 |
| General and Administrative Expense [Member] | ||
| Stock-based compensation expense | $ 640 | $ 562 |
| X | ||||||||||
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
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| X | ||||||||||
- Details
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| X | ||||||||||
- Details
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