Note 12 - Investment Securities - Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Held to maturity investments, less than one year	$ 19,420	$ 19,793
Held to maturity investments for one to five years	4,558	5,085
Held to maturity, total	23,978	24,878
Commercial Paper Original Maturities of 91 Days or More [Member]
Held to maturity investments, less than one year	10,987	7,490
Held to maturity investments for one to five years	0	0
Held to maturity, total	10,987	7,490
Corporate Notes And Bonds [Member]
Held to maturity investments, less than one year	8,433	12,303
Held to maturity investments for one to five years	4,558	5,085
Held to maturity, total	$ 12,991	$ 17,388

Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (d)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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