Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Short-term marketable securities	$ 5,552	$ 6,397
Long-term Securities	601	781
Fair Value, Nonrecurring [Member]
Cost Basis	6,703	8,584
Unrealized Loss	(40)	90
Unrealized Loss	40	(90)
Fair Value	6,663	8,494
Cash Equivalents	510	1,316
Short-term marketable securities	5,552	6,397
Long-term Securities	601	781
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Nonrecurring [Member]
Cost Basis	510	1,316
Unrealized Loss	0	0
Unrealized Loss	(0)	0
Fair Value	510	1,316
Cash Equivalents	510	1,316
Short-term marketable securities		0
Long-term Securities		0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member]
Cost Basis	6,193	7,268
Unrealized Loss	(40)	90
Unrealized Loss	40	(90)
Fair Value	6,153	7,178
Cash Equivalents	0	0
Short-term marketable securities	5,552	6,397
Long-term Securities	601	781
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Certificates of Deposit [Member]
Cost Basis	302	800
Unrealized Loss	0	0
Unrealized Loss	(0)	0
Fair Value	302	800
Cash Equivalents	0	0
Short-term marketable securities	0	498
Long-term Securities	302	302
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Cost Basis	3,694	4,066
Unrealized Loss	(28)	65
Unrealized Loss	28	(65)
Fair Value	3,666	4,001
Cash Equivalents	0	0
Short-term marketable securities	3,367	3,772
Long-term Securities	299	229
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Corporate Debt Securities [Member]
Cost Basis	2,197	2,402
Unrealized Loss	(12)	25
Unrealized Loss	12	(25)
Fair Value	2,185	2,377
Cash Equivalents	0	0
Short-term marketable securities	2,185	2,127
Long-term Securities	$ 0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Convertible Debt Securities [Member]
Long-term Securities		$ 250

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)
-Publisher FASB
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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
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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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
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amount of investment in marketable security, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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Amount of investment in marketable security, classified as noncurrent.

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