Operating Segment Information - Segment earnings before income taxes to earnings before income taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Reconciliation of earnings before income taxes
Net investment income	$ 42,321	$ 36,726
Net realized gains	9,559	14,912
Net unrealized gains (losses) on equity securities	(39,396)	(42,318)
Interest expense on debt	(2,353)	(1,335)
General corporate expense	(2,724)	(2,948)
Equity in earnings of unconsolidated investees	2,147	3,048
Earnings before income taxes	67,341	78,631
Operating Segments
Reconciliation of earnings before income taxes
Net investment income	42,321	36,726
Net realized gains	9,559	14,912
Net unrealized gains (losses) on equity securities	(39,396)	(42,318)
Earnings before income taxes	57,787	70,546
Corporate
Reconciliation of earnings before income taxes
Net investment income	42,321	36,726
Net realized gains	9,559	14,912
Net unrealized gains (losses) on equity securities	(39,396)	(42,318)
Interest expense on debt	(2,353)	(1,335)
General corporate expense	(2,724)	(2,948)
Equity in earnings of unconsolidated investees	$ 2,147	$ 3,048