Note 6 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Cash Equivalents	$ 1,437
Short-term marketable securities	3,011	$ 1,481
Fair Value, Nonrecurring [Member]
Cost Basis	4,451	3,798
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(3)	(10)
Fair Value	4,448	3,788
Cash Equivalents	1,437	2,307
Short-term marketable securities	3,011	1,481
Long-term Securities	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Cost Basis	1,437	2,307
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	1,437	2,307
Cash Equivalents		2,307
Short-term marketable securities		0
Long-term Securities		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Cost Basis	3,014	1,491
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(3)	(10)
Fair Value	3,011	1,481
Cash Equivalents	0	0
Short-term marketable securities	3,011	1,481
Long-term Securities	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Certificates of Deposit [Member]
Cost Basis	552	301
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	552	301
Cash Equivalents	0	0
Short-term marketable securities	552	301
Long-term Securities	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Cost Basis	1,105	926
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(1)	(7)
Fair Value	1,104	919
Cash Equivalents	0	0
Short-term marketable securities	1,104	919
Long-term Securities	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Corporate Debt Securities [Member]
Cost Basis	1,357	264
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(2)	(3)
Fair Value	1,355	261
Cash Equivalents	0	0
Short-term marketable securities	1,355	261
Long-term Securities	$ 0	$ 0