Investments (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
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 480,529	$ 225,588	$ 1,259,084	$ 620,551
Less: investment expenses	(19,665)	(14,826)	(55,695)	(38,361)
Net investment income	460,864	210,762	1,203,389	582,190
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	3,886	3,077	9,206	4,429
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	58,673	29,682	163,646	74,731
Policy loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15,962	5,354	31,580	15,573
Other invested assets
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	36,152	7,109	77,875	82,142
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	27,347	14,444	88,105	18,533
Available-for-sale | Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	312,405	153,170	822,933	384,347
Trading | Fixed maturities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 26,104	$ 12,752	$ 65,739	$ 40,796