Note 3 - Investments - Summary of Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Investments, amortized cost	$ 15,047	$ 14,932
Investments, unrealized gains	4	4
Investments, unrealized losses	0	(15)
Investments, fair value	15,051	14,921
Investments, unrealized losses	(0)	15
Corporate Debt Securities [Member]
Investments, amortized cost	11,375	11,310
Investments, unrealized gains	2	0
Investments, unrealized losses	0	(15)
Investments, fair value	11,377	11,295
Investments, unrealized losses	(0)	15
US Treasury and Government Short-Term Debt Securities [Member]
Investments, amortized cost	3,672	3,622
Investments, unrealized gains	2	4
Investments, unrealized losses	0	0
Investments, fair value	3,674	3,626
Investments, unrealized losses	$ 0	$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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