Note 2 - Investments - Security Holdings in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	$ 104,105	$ 354,769
Less than 12 Months, Accumulated Loss	(2,482)	(8,726)
12 Months or Longer, fair value	264,694	309,203
12 Months or Longer, Accumulated Loss	(18,523)	(28,531)
Fair value	368,799	663,972
Accumulated Loss	(21,005)	(37,257)
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	1,600	16,507
Less than 12 Months, Accumulated Loss	(45)	(65)
12 Months or Longer, fair value	8,161	14,291
12 Months or Longer, Accumulated Loss	(234)	(584)
Fair value	9,761	30,798
Accumulated Loss	(279)	(649)
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	5,181	2,614
Less than 12 Months, Accumulated Loss	(541)	(419)
12 Months or Longer, fair value	9,342	5,076
12 Months or Longer, Accumulated Loss	(637)	(438)
Fair value	14,523	7,690
Accumulated Loss	(1,178)	(857)
Special Revenue Excluding Asset Backed Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	230	2,182
Less than 12 Months, Accumulated Loss	(7)	(426)
12 Months or Longer, fair value	14,939	21,733
12 Months or Longer, Accumulated Loss	(2,118)	(3,308)
Fair value	15,169	23,915
Accumulated Loss	(2,125)	(3,734)
Corporate Debt Securities and Other Debt Obligations [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	61,100	181,179
Less than 12 Months, Accumulated Loss	(1,392)	(4,996)
12 Months or Longer, fair value	143,594	176,531
12 Months or Longer, Accumulated Loss	(7,134)	(13,353)
Fair value	204,694	357,710
Accumulated Loss	(8,526)	(18,349)
Asset-Backed Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	35,994	152,287
Less than 12 Months, Accumulated Loss	(497)	(2,820)
12 Months or Longer, fair value	88,658	91,572
12 Months or Longer, Accumulated Loss	(8,400)	(10,848)
Fair value	124,652	243,859
Accumulated Loss	$ (8,897)	$ (13,668)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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