Liability For Future Policy Benefits (Additional Insurance Reserves) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Insurance [Abstract]
Balance, including amounts in AOCI, post-flooring	$ 14,280,793	$ 12,664,445
Flooring impact and amounts in AOCI	831,583	1,269,237
Balance, excluding amounts in AOCI, beginning of period, pre-flooring	15,112,376	13,933,682
Effect of assumption update			$ 154,058	$ 22,910
Effect of actual variances from expected experience and other activity			326,790	(12,611)
Adjusted balance, beginning of period			$ 15,593,224	$ 13,943,981
Assessments collected	843,853	828,657
Interest accrual	397,904	360,309
Benefits paid	(258,579)	(219,784)
Balance, excluding amounts in AOCI, end of period, pre-flooring	16,576,402	14,913,163
Flooring impact and amounts in AOCI	(343,625)	(1,714,686)
Balance, including amounts in AOCI, end of period, post-flooring	16,232,777	13,198,477
Less: Reinsurance recoverables	16,005,948	12,979,687
Balance after reinsurance recoverables, including amounts in AOCI, end of period	$ 226,829	$ 218,790
Weighted-average duration of the liability in years (at original discount rate)	22 years	22 years
Weighted-average interest rate (at original discount rate)	3.39%	3.36%