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Note 7 - Investment and Equity Securities (Details Textual)		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Equity Securities, FV-NI, Current		$ 833,000		$ 833,000		$ 609,000
Equity Securities, FV-NI, Unrealized Gain (Loss), Total	[1]	102,000	$ (28,000)	223,000	$ (157,000)
Equity Securities, FV-NI, Realized Gain (Loss), Total		0	$ 0	0	0
Security Owned and Pledged as Collateral, Fair Value, Total		$ 72,700,000		$ 72,700,000		71,100,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions		30		30
Available-for-sale Securities, Percentage of Portfolio		80.00%		80.00%
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total				$ 0	$ 0	$ 0
[1] Not within scope of ASC 606

X

- Definition

Represents a percentage of the available-for-sale securities portfolio.

+ References

No definition available.

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- Definition

Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

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- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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- Definition

Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings and other comprehensive loss (OCI).

+ References

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- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
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