Note 3 - Investment Securities - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2023	Dec. 31, 2022
Gross unrealized holding gains		$ 0
Gross unrealized holding losses		1,482
Estimated fair value	$ 78,024	70,296
Amortized cost, as adjusted		71,778
Short-Term Investments [Member]
Gross unrealized holding gains	10
Gross unrealized holding losses	243
Amortized cost, as adjusted	78,257
US Government Agencies Debt Securities [Member] \| Short-Term Investments [Member]
Gross unrealized holding gains	10	0
Gross unrealized holding losses	243	1,053
Estimated fair value	$ 78,024	58,321
Amortized cost, as adjusted		59,374
US Government Agencies Debt Securities [Member] \| Short-Term Investments [Member] \| Minimum [Member]
Maturity date	Oct. 31, 2023
US Government Agencies Debt Securities [Member] \| Long Term Investments [Member]
Gross unrealized holding gains		0
Gross unrealized holding losses		429
Estimated fair value		11,975
Amortized cost, as adjusted		$ 12,404

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

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