Note 3 - Marketable Securities - Fair Value and Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair value, less than 12 months	$ 136	$ 47,029
Gross unrealized loss, less than 12 months	0	(40)
Fair value, greater than 12 months	0	0
Gross unrealized loss, greater than 12 months	0	0
Corporate Debt Securities [Member]
Fair value, less than 12 months	0	32,529
Gross unrealized loss, less than 12 months	0	(36)
Fair value, greater than 12 months	0	0
Gross unrealized loss, greater than 12 months	0	0
Commercial Paper [Member]
Fair value, less than 12 months	0	8,891
Gross unrealized loss, less than 12 months	0	0
Fair value, greater than 12 months	0	0
Gross unrealized loss, greater than 12 months	0	0
Money Market Funds [Member]
Fair value, less than 12 months	136	3,686
Gross unrealized loss, less than 12 months	0	0
Fair value, greater than 12 months	0	0
Gross unrealized loss, greater than 12 months	0	0
Debt Security, Corporate, Non-US [Member]
Fair value, less than 12 months	0	1,923
Gross unrealized loss, less than 12 months	0	(4)
Fair value, greater than 12 months	0	0
Gross unrealized loss, greater than 12 months	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563

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-Name Accounting Standards Codification
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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, 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 7
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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