Note 4 - Short-term Investments - Summary of Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Investments, amortized cost	$ 30,170	$ 14,932
Investments, unrealized gains	57	4
Investments, unrealized losses	0	(15)
Investments, fair value	30,227	14,921
Corporate Debt Securities [Member]
Investments, amortized cost	21,814	11,310
Investments, unrealized gains	35	0
Investments, unrealized losses	0	(15)
Investments, fair value	21,849	11,295
US Treasury and Government Short-Term Debt Securities [Member]
Investments, amortized cost	8,356	3,622
Investments, unrealized gains	22	4
Investments, unrealized losses	0	0
Investments, fair value	$ 8,378	$ 3,626