Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Net Investment Income [Line Items]
Gross investment income	$ 381,851	$ 374,975	$ 745,615	$ 697,057
Investment expense	(2,548)	(2,846)	(6,020)	(5,090)
Net investment income	379,303	372,129	739,595	691,967
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	322,518	324,136	636,306	659,384
Investment funds
Net Investment Income [Line Items]
Gross investment income	27,268	25,476	54,291	(3,873)
Arbitrage Trading Account
Net Investment Income [Line Items]
Gross investment income	23,672	16,682	40,001	34,693
Equity securities
Net Investment Income [Line Items]
Gross investment income	12,485	12,386	23,126	23,721
Real estate
Net Investment Income [Line Items]
Gross investment income	$ (4,092)	$ (3,705)	$ (8,109)	$ (16,868)