Investments - Schedule of Analysis of Investment Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net Investment Income [Line Items]
Investment income, gross	$ 287,025	$ 261,392
Percentage change in investment income, gross	10.00%
Less investment expense	$ (4,447)	(4,287)
Percentage change in investment expense	4.00%
Net investment income	$ 282,578	257,105
Percentage change in net investment income	10.00%
Fixed maturities available for sale
Net Investment Income [Line Items]
Investment income, gross	$ 246,098	232,299
Percentage change in investment income, gross	6.00%
Policy loans
Net Investment Income [Line Items]
Investment income, gross	$ 12,816	11,755
Percentage change in investment income, gross	9.00%
Mortgage loans
Net Investment Income [Line Items]
Investment income, gross	$ 6,760	4,003
Percentage change in investment income, gross	69.00%
Other long-term investments
Net Investment Income [Line Items]
Investment income, gross	$ 19,663	11,740
Percentage change in investment income, gross	67.00%
Short-term investments
Net Investment Income [Line Items]
Investment income, gross	$ 1,688	1,595
Percentage change in investment income, gross
Fair value option
Net Investment Income [Line Items]
Net investment income	$ 18,900	$ 11,300