Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Short-term marketable securities	$ 1,481	$ 6,397
Certificates of deposit	0	781
Fair Value, Nonrecurring [Member]
Cost basis	3,798	8,584
Unrealized loss	(10)	90
Money market funds	10	(90)
Fair value	3,788	8,494
Cash equivalents	2,307	1,316
Short-term marketable securities	1,481	6,397
Certificates of deposit	0	781
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Nonrecurring [Member]
Cost basis	2,307	1,316
Unrealized loss	0	0
Money market funds	(0)	0
Fair value	2,307	1,316
Cash equivalents	2,307	1,316
Short-term marketable securities		0
Certificates of deposit		0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member]
Cost basis	1,491	7,268
Unrealized loss	(10)	90
Money market funds	10	(90)
Fair value	1,481	7,178
Cash equivalents	0	0
Short-term marketable securities	1,481	6,397
Certificates of deposit	0	781
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Certificates of Deposit [Member]
Cost basis	301	800
Unrealized loss	0	0
Money market funds	(0)	0
Fair value	301	800
Cash equivalents	0	0
Short-term marketable securities	301	498
Certificates of deposit	0	302
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Cost basis	926	4,066
Unrealized loss	(7)	65
Money market funds	7	(65)
Fair value	919	4,001
Cash equivalents	0	0
Short-term marketable securities	919	3,772
Certificates of deposit	0	229
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Corporate Debt Securities [Member]
Cost basis		2,402
Unrealized loss		25
Money market funds		(25)
Fair value		2,377
Cash equivalents		0
Short-term marketable securities		2,127
Certificates of deposit		$ 250
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Corporate Segment [Member]
Cost basis	264
Unrealized loss	(3)
Money market funds	3
Fair value	261
Cash equivalents	0
Short-term marketable securities	261
Certificates of deposit	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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-Paragraph 1
-Publisher FASB
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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No definition available.

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Amount, before tax, of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Publisher FASB
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Amount of investment in marketable security, classified as current.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
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Amount of investment in marketable security, classified as noncurrent.

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