Note 2 - Summary of Significant Accounting Policies - Noncash Stock-based Compensation Expense (Details) - USD ($)  | 
3 Months Ended | |
|---|---|---|
Mar. 31, 2024  | 
Mar. 31, 2023  | 
|
| Noncash stock compensation expense | $ 332,000 | $ 783,000 | 
| Selling and Marketing Expense [Member] | ||
| Noncash stock compensation expense | 122,000 | 164,000 | 
| Research and Development Expense [Member] | ||
| Noncash stock compensation expense | 11,000 | 89,000 | 
| General and Administrative Expense [Member] | ||
| Noncash stock compensation expense | $ 199,000 | $ 530,000 | 
| X | ||||||||||
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
- Details 
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| X | ||||||||||
- Details 
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| X | ||||||||||
- Details 
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