Operating Segment Information - Segment earnings before income taxes to earnings before income taxes (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Reconciliation of earnings before income taxes
Net investment income	$ 46,694	$ 41,270	$ 135,057	$ 117,414
Net realized gains	8,637	18,318	27,603	48,234
Net unrealized gains (losses) on equity securities	(3,282)	41,981	60,346	43,163
Interest expense on debt	(4,200)	(1,364)	(10,994)	(4,049)
General corporate expense	(3,388)	(5,045)	(12,335)	(12,747)
Equity in earnings of unconsolidated investees	(3,137)	1,540	1,980	7,055
Earnings before income taxes	100,093	157,245	378,122	392,391
Operating Segments
Reconciliation of earnings before income taxes
Net investment income	46,694	41,270	135,057	117,414
Net realized gains	8,637	18,318	27,603	48,234
Net unrealized gains (losses) on equity securities	(3,282)	41,981	60,346	43,163
Earnings before income taxes	58,769	60,545	176,465	193,321
Corporate
Reconciliation of earnings before income taxes
Net investment income	46,694	41,270	135,057	117,414
Net realized gains	8,637	18,318	27,603	48,234
Net unrealized gains (losses) on equity securities	(3,282)	41,981	60,346	43,163
Interest expense on debt	(4,200)	(1,364)	(10,994)	(4,049)
General corporate expense	(3,388)	(5,045)	(12,335)	(12,747)
Equity in earnings of unconsolidated investees	$ (3,137)	$ 1,540	$ 1,980	$ 7,055

General corporate expenses.

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