Note 4 - Fair Value of Financial Instruments - Fair Value by Hierarchy (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Total assets	$ 30,448	$ 14,921
Fair Value, Inputs, Level 1 [Member]
Total assets	0	0
Fair Value, Inputs, Level 2 [Member]
Total assets	30,448	14,921
Fair Value, Inputs, Level 3 [Member]
Total assets	0	0
Corporate Debt Securities [Member]
Short term investment	21,923	11,295
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Short term investment	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Short term investment	21,923	11,295
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Short term investment	0	0
US Treasury and Government Short-Term Debt Securities [Member]
Short term investment	8,525	3,626
US Treasury and Government Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Short term investment		0
US Treasury and Government Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Short term investment	$ 8,525	3,626
US Treasury and Government Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Short term investment		$ 0