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Note 4 - Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Sep. 30, 2024
--- | --- | ---
Fair value | $ 124,477 | $ 139,330
Short-term US Treasury Securities [Member] |  |
Amortized cost | 82,005 | 113,987
Unrealized gains | 215 | 382
Unrealized losses | (159) | (45)
Fair value | 82,061 | 114,324
Short-term Certificates of Deposit [Member] |  |
Amortized cost | 500 | 500
Unrealized gains | 0 | 1
Unrealized losses | 0 | 0
Fair value | 500 | 501
Short-term Investment [Member] |  |
Amortized cost | 82,505 | 114,487
Unrealized gains | 215 | 383
Unrealized losses | (159) | (45)
Fair value | 82,561 | 114,825
US Treasury Securities [Member] |  |
Amortized cost |  | 24,514
Unrealized gains |  | 0
Unrealized losses |  | (245)
Fair value |  | 24,269
Long-term Certificates of Deposit [Member] |  |
Amortized cost | 248 | 248
Unrealized gains | 0 | 0
Unrealized losses | (11) | (12)
Fair value | 237 | 236
Long-term Investment [Member] |  |
Amortized cost | 42,049 | 24,762
Unrealized gains | 14 | 0
Unrealized losses | (147) | (257)
Fair value | 41,916 | $ 24,505
Long-term US Treasury Securities [Member] |  |
Amortized cost | 41,801 |
Unrealized gains | 14 |
Unrealized losses | (136) |
Fair value | $ 41,679 |

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