Net Investment Income (Net Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Investment Income [Line Items]
Gross investment income	$ 1,343,815	$ 1,059,751	$ 789,106
Investment expense	(10,654)	(6,916)	(9,921)
Net investment income	1,333,161	1,052,835	779,185
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	1,260,429	929,098	549,281
Investment funds
Net Investment Income [Line Items]
Gross investment income	(11,491)	16,743	145,099
Arbitrage trading account (1)
Net Investment Income [Line Items]
Gross investment income	69,573	69,369	45,213
Real estate
Net Investment Income [Line Items]
Gross investment income	(23,616)	(11,185)	(3,087)
Equity securities
Net Investment Income [Line Items]
Gross investment income	$ 48,920	$ 55,726	$ 52,600