Note 4 - Fair Value of Financial Instruments - Fair Value by Hierarchy (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Total assets	$ 15,051	$ 14,921
Fair Value, Inputs, Level 1 [Member]
Total assets	0	0
Fair Value, Inputs, Level 2 [Member]
Total assets	15,051	14,921
Fair Value, Inputs, Level 3 [Member]
Total assets	0	0
Corporate Debt Securities [Member]
Short term investment	11,377	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	11,377	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	3,674	3,626
US Treasury and Government Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Short term investment	$ 3,674	$ 3,626