Note 4 - Marketable Securities - Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Amortized Cost	$ 149,981	$ 151,965
Unrealized Gains	12	64
Unrealized Losses	(519)	(366)
Marketable Securities	149,474	151,663
Corporate Debt Securities [Member]
Amortized Cost	48,885	87,998
Unrealized Gains	10	12
Unrealized Losses	(250)	(250)
Marketable Securities	48,645	87,760
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Amortized Cost	50,637	37,680
Unrealized Gains	0	33
Unrealized Losses	(43)	(31)
Marketable Securities	50,594	37,682
Certificates of Deposit [Member]
Amortized Cost	26,515	19,689
Unrealized Gains	2	16
Unrealized Losses	(34)	(38)
Marketable Securities	26,483	19,667
US Treasury Securities [Member]
Amortized Cost	14,932
Unrealized Gains	0
Unrealized Losses	(154)
Marketable Securities	14,778
Asset-Backed Securities [Member]
Amortized Cost	9,012	6,598
Unrealized Gains	0	3
Unrealized Losses	(38)	(47)
Marketable Securities	$ 8,974	$ 6,554

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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