Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net Investment Income [Line Items]
Gross investment income	$ 272,781	$ 205,143	$ 745,705	$ 554,252
Investment expense	(1,837)	(2,327)	(6,211)	(6,350)
Net investment income	270,944	202,816	739,494	547,902
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	239,727	146,051	653,200	371,724
Arbitrage trading account (1)
Net Investment Income [Line Items]
Gross investment income	4,450	36,045	5,444	121,919
Equity securities
Net Investment Income [Line Items]
Gross investment income	12,714	14,650	41,714	38,303
Investment funds
Net Investment Income [Line Items]
Gross investment income	17,876	10,694	53,168	24,008
Real estate
Net Investment Income [Line Items]
Gross investment income	$ (1,986)	$ (2,297)	$ (7,821)	$ (1,702)