Note 3 - Investments - Summary of Available for Sale Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Available-for-Sale, Amortized Cost	$ 675,130	$ 561,580
Available-for-sale, Accumulated Gross Unrealized Gain	3,876	407
Available-for-sale, Accumulated Gross Unrealized Loss	(34,303)	(46,687)
Available-for-Sale, Allowance for Credit Loss	(904)	(236)
Debt Securities, Available-for-sale	643,799	515,064
US Government Agencies Debt Securities [Member]
Available-for-Sale, Amortized Cost	40,836	50,802
Available-for-sale, Accumulated Gross Unrealized Gain	0	2
Available-for-sale, Accumulated Gross Unrealized Loss	(1,416)	(2,253)
Available-for-Sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	39,420	48,551
US States and Political Subdivisions Debt Securities [Member]
Available-for-Sale, Amortized Cost	10,641	10,776
Available-for-sale, Accumulated Gross Unrealized Gain	100	49
Available-for-sale, Accumulated Gross Unrealized Loss	(839)	(1,173)
Available-for-Sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	9,902	9,652
Special Revenue Excluding Asset Backed Securities [Member]
Available-for-Sale, Amortized Cost	32,513	37,260
Available-for-sale, Accumulated Gross Unrealized Gain	147	26
Available-for-sale, Accumulated Gross Unrealized Loss	(3,149)	(4,487)
Available-for-Sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	29,511	32,799
Corporate Debt Securities and Other Debt Obligations [Member]
Available-for-Sale, Amortized Cost	316,590	278,164
Available-for-sale, Accumulated Gross Unrealized Gain	1,750	79
Available-for-sale, Accumulated Gross Unrealized Loss	(17,197)	(23,912)
Available-for-Sale, Allowance for Credit Loss	(904)	(236)
Debt Securities, Available-for-sale	300,239	254,095
Asset-Backed Securities [Member]
Available-for-Sale, Amortized Cost	274,550	184,578
Available-for-sale, Accumulated Gross Unrealized Gain	1,879	251
Available-for-sale, Accumulated Gross Unrealized Loss	(11,702)	(14,862)
Available-for-Sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale	$ 264,727	$ 169,967

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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