Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Short-term marketable securities	$ 6,551	$ 6,397
Long-term Securities	1,034	781
Fair Value, Nonrecurring [Member]
Cost Basis	8,631	8,584
Unrealized Gains (Losses)	(69)	90
Unrealized Gains (Losses)	69	(90)
Fair Value	8,562	8,494
Cash Equivalents	977	1,316
Short-term marketable securities	6,551	6,397
Long-term Securities	1,034	781
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Nonrecurring [Member]
Cost Basis	977	1,316
Unrealized Gains (Losses)	0	0
Unrealized Gains (Losses)	(0)	0
Fair Value	977	1,316
Cash Equivalents	977	1,316
Short-term marketable securities		0
Long-term Securities		0
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member]
Cost Basis	7,654	7,268
Unrealized Gains (Losses)	(69)	90
Unrealized Gains (Losses)	69	(90)
Fair Value	7,585	7,178
Cash Equivalents	0	0
Short-term marketable securities	6,551	6,397
Long-term Securities	1,034	781
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Certificates of Deposit [Member]
Cost Basis	800	800
Unrealized Gains (Losses)	0	0
Unrealized Gains (Losses)	(0)	0
Fair Value	800	800
Cash Equivalents	0	0
Short-term marketable securities	498	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	4,645	4,066
Unrealized Gains (Losses)	(49)	65
Unrealized Gains (Losses)	49	(65)
Fair Value	4,596	4,001
Cash Equivalents	0	0
Short-term marketable securities	4,116	3,772
Long-term Securities	480	229
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Nonrecurring [Member] \| Corporate Debt Securities [Member]
Cost Basis	2,209	2,402
Unrealized Gains (Losses)	(20)	25
Unrealized Gains (Losses)	20	(25)
Fair Value	2,189	2,377
Cash Equivalents	0	0
Short-term marketable securities	1,937	2,127
Long-term Securities	$ 252
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

No definition available.

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of investment in marketable security, classified as current.

+ References

No definition available.

+ Details

Name:	us-gaap_MarketableSecuritiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in marketable security, classified as noncurrent.

+ References

No definition available.

+ Details

Name:	us-gaap_MarketableSecuritiesNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_ConvertibleDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: