Note 6 - Fair Value Measurements - Fair Value Hierarchy for Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Corporate and municipal debt securities	$ 5,099	$ 4,973
Total assets	32,810
Corporate Debt Securities [Member]
Corporate and municipal debt securities	5,099
Money Market Funds [Member]
Money market accounts	27,711
Fair Value, Inputs, Level 1 [Member]
Total assets	32,810
Fair Value, Inputs, Level 1 [Member] \| Corporate Debt Securities [Member]
Corporate and municipal debt securities	5,099
Fair Value, Inputs, Level 1 [Member] \| Money Market Funds [Member]
Money market accounts	$ 27,711

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-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 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481830/320-10-45-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

Reference 4: 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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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant