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, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Statement Of Income Captions [Line Items]
Net investment income	$ 86,078	$ 68,862	$ 67,893
Net realized (gains) losses	588,515	64,222	17,885
Equity in earnings of unconsolidated investees	9,853	37,060	20,233
Interest on debt	(8,047)	(7,677)	(7,603)
Earnings (losses) before income taxes	720,678	344,321	189,841
Income tax expense	137,267	64,967	32,750
Net earnings (losses)	583,411	279,354	157,091
Unrealized gains (losses) on securities:
Net current-period other comprehensive earnings (loss)	(278,902)	(58,888)	56,219
Comprehensive earnings	304,509	220,466	213,310
Parent Company
Condensed Statement Of Income Captions [Line Items]
Net investment income	6,245	2,102	1,412
Net realized (gains) losses	570,888	(625)	501
Equity in earnings of unconsolidated investees	372	22,786	10,368
Selling, general and administrative expenses	(12,900)	(13,330)	(10,265)
Interest on debt	(7,622)	(7,616)	(7,603)
Earnings (losses) before income taxes	556,983	3,317	(5,587)
Income tax expense	108,699	(1,585)	(2,885)
Net earnings (loss) before equity in net earnings of subsidiaries	448,284	4,902	(2,702)
Equity in net earnings of subsidiaries	135,127	274,452	159,793
Net earnings (losses)	583,411	279,354	157,091
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during the period	(12,188)	(1,996)	994
Less: reclassification adjustment for (gains) losses included in net earnings	115	500	(390)
Other comprehensive earnings (loss) - parent only	(12,073)	(1,496)	604
Equity in other comprehensive earnings (loss) of subsidiaries/investees	(266,829)	(57,392)	55,615
Net current-period other comprehensive earnings (loss)	(278,902)	(58,888)	56,219
Comprehensive earnings	$ 304,509	$ 220,466	$ 213,310