Note 2 - Investments - Security Holdings in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	$ 662,490	$ 104,439
Less than 12 Months, Accumulated Loss	(8,411)	(1,833)
12 Months or Longer, fair value	241,964	270,911
12 Months or Longer, Accumulated Loss	(19,660)	(17,678)
Fair value	904,454	375,350
Accumulated Loss	(28,071)	(19,511)
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	14,362	2,006
Less than 12 Months, Accumulated Loss	(122)	(38)
12 Months or Longer, fair value	6,675	5,704
12 Months or Longer, Accumulated Loss	(224)	(188)
Fair value	21,037	7,710
Accumulated Loss	(346)	(226)
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	1,698	5,157
Less than 12 Months, Accumulated Loss	(37)	(441)
12 Months or Longer, fair value	11,872	9,509
12 Months or Longer, Accumulated Loss	(918)	(553)
Fair value	13,570	14,666
Accumulated Loss	(955)	(994)
Special Revenue Excluding Asset Backed Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	999	0
Less than 12 Months, Accumulated Loss	(18)	0
12 Months or Longer, fair value	15,277	15,185
12 Months or Longer, Accumulated Loss	(1,769)	(1,887)
Fair value	16,276	15,185
Accumulated Loss	(1,787)	(1,887)
Corporate Debt Securities and Other Debt Obligations [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	325,212	49,963
Less than 12 Months, Accumulated Loss	(5,188)	(948)
12 Months or Longer, fair value	137,030	160,780
12 Months or Longer, Accumulated Loss	(8,412)	(7,456)
Fair value	462,242	210,743
Accumulated Loss	(13,600)	(8,404)
Asset-Backed Securities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 Months, fair value	320,219	47,313
Less than 12 Months, Accumulated Loss	(3,046)	(406)
12 Months or Longer, fair value	71,110	79,733
12 Months or Longer, Accumulated Loss	(8,337)	(7,594)
Fair value	391,329	127,046
Accumulated Loss	$ (11,383)	$ (8,000)

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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