Liability for Future Policy Benefits (Additional Insurance Reserves) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance [Abstract]
Balance including amounts in AOCI, beginning of period, post-flooring	$ 14,280,792	$ 12,664,445	$ 11,660,527
Flooring Impact and amounts in AOCI	831,583	1,269,236	(896,931)
Balance, excluding amounts in AOCI, beginning of period, pre-flooring		15,112,375	13,933,681	$ 10,763,596
Effect of assumption updates		154,058	22,910	2,197,592
Effect of actual variance from expected experience and other activity		265,684	34,021	(223,185)
Adjusted balance, beginning of period		15,532,117	13,990,612	$ 12,738,003
Assessments collected	1,242,684	929,709	961,924
Interest accrual	536,678	486,253	433,631
Benefits paid	(343,241)	(294,199)	(199,877)
Balance, excluding amounts in AOCI, end of period, pre-flooring	16,968,238	15,112,375	13,933,681
Flooring Impact and amounts in AOCI	(617,186)	(831,583)	(1,269,236)
Balance, including amounts in AOCI, end of period, post-flooring	16,351,052	14,280,792	12,664,445
Less: Reinsurance recoverable	16,129,846	14,054,600	12,458,184
Balance after reinsurance recoverable, including amounts in AOCI, end of period	$ 221,206	$ 226,192	$ 206,261
Weighted-average duration of the liability in years (at original discount rate)	22 years	22 years	23 years
Weighted-average interest rate (at original discount rate)	3.33%	3.39%	3.37%