Schedule II - Condensed Financial Information of Registrant (Parent Company) - Condensed Statements of Earnings and Comprehensive Earnings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Statement Of Income Captions [Line Items]
Net investment income	$ 120,383	$ 86,078	$ 68,862
Net realized gains (losses)	32,518	588,515	64,222
Equity in earnings of unconsolidated investees	9,610	9,853	37,060
Interest on debt	(7,301)	(8,047)	(7,677)
Earnings before income taxes	377,265	720,678	344,321
Income tax expense (benefit)	72,654	137,267	64,967
Net earnings	304,611	583,411	279,354
Unrealized gains (losses) on securities:
Other comprehensive earnings (loss)	62,773	(278,902)	(58,888)
Comprehensive earnings	367,384	304,509	220,466
Parent Company
Condensed Statement Of Income Captions [Line Items]
Net investment income	10,351	6,245	2,102
Net realized gains (losses)	14,134	570,888	(625)
Equity in earnings of unconsolidated investees		372	22,786
Selling, general and administrative expenses	(15,917)	(12,900)	(13,330)
Interest on debt	(6,543)	(7,622)	(7,616)
Earnings before income taxes	2,025	556,983	3,317
Income tax expense (benefit)	(1,802)	108,699	(1,585)
Net earnings before equity in net earnings of subsidiaries	3,827	448,284	4,902
Equity in net earnings of subsidiaries	300,784	135,127	274,452
Net earnings	304,611	583,411	279,354
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during the period	1,754	(12,188)	(1,996)
Less: reclassification adjustment for (gains) losses included in net earnings		115	500
Other comprehensive earnings (loss) - parent only	1,754	(12,073)	(1,496)
Equity in other comprehensive earnings (loss) of subsidiaries/investees	61,019	(266,829)	(57,392)
Other comprehensive earnings (loss)	62,773	(278,902)	(58,888)
Comprehensive earnings	$ 367,384	$ 304,509	$ 220,466