Note 3 - Short-term Investments - Summary of Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024
Investments, amortized cost	$ 20,641	$ 30,170
Investments, unrealized gains	14	57
Investments, unrealized losses	0	0
Investments, fair value	20,655	30,227
Corporate Debt Securities [Member]
Investments, amortized cost	16,899	21,814
Investments, unrealized gains	7	35
Investments, unrealized losses	0	0
Investments, fair value	16,906	21,849
US Treasury and Government Short-Term Debt Securities [Member]
Investments, amortized cost	3,742	8,356
Investments, unrealized gains	7	22
Investments, unrealized losses	0	0
Investments, fair value	$ 3,749	$ 8,378