Note 4 - Fair Value Measurements - Assets Categorized on Basis of Various Levels (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Assets, fair value	$ 58,643	$ 54,234
Money Market Funds [Member]
Assets, fair value	58,633	54,225
Mutual Fund Investment [Member]
Assets, fair value	10	9
Cash and Cash Equivalents [Member]
Assets, fair value	58,633	54,225
Marketable Securities [Member]
Assets, fair value	10	9
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	58,643	54,234
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets, fair value	58,633	54,225
Fair Value, Inputs, Level 1 [Member] | Mutual Fund Investment [Member]
Assets, fair value	10	9
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Assets, fair value	58,633	54,225
Fair Value, Inputs, Level 1 [Member] | Marketable Securities [Member]
Assets, fair value	10	9
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Mutual Fund Investment [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Marketable Securities [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Mutual Fund Investment [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Assets, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Marketable Securities [Member]
Assets, fair value	$ 0	$ 0