Note 4 - Fair Value Measurements - Fair Value of Assets and Liabilities Measured On Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Reported Value Measurement [Member]
Cash and cash equivalents	$ 13,331	$ 24,739
Restricted cash	25	25
Ownership interests	860	4,549
Reported Value Measurement [Member] \| US Treasury Securities [Member]
U.S. Government securities	5,956
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	13,331	24,739
Restricted cash	25	25
Ownership interests	860	4,549
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member]
U.S. Government securities	5,956
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Ownership interests	0	0
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member]
U.S. Government securities	0
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Ownership interests	0	$ 0
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| US Treasury Securities [Member]
U.S. Government securities	$ 0

Fair value portion of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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.

No definition available.

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- Definition

Amount of fair value for investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

No definition available.

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- 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.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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

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