Liability for Future Policyholder Benefits - Reconciliation of the Net Liability for Future Benefits to Life and Health Insurance Reserves (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Insurance [Abstract]
Net Liability for Future Policyholder Benefits, post-flooring	$ 2,897,500	$ 2,644,100	$ 2,897,500	$ 2,644,100
Deferred Profit Liability	390,600	304,900	390,600	304,900	$ 337,800	$ 253,600
A&H and Other Reserves	137,700	149,100	137,700	149,100
Total Life and Health Insurance Reserves	3,425,800	3,098,100	3,425,800	3,098,100
Term Life Insurance
Insurance [Abstract]
Gross Premiums or Assessments	99,800	98,400	300,300	300,700
Interest Expense	35,000	35,400	104,700	106,100
Liability for Future Policy Benefit, by Product Segment [Line Items]
Net Liability for Future Policyholder Benefits, post-flooring	10,274,000	10,181,500	10,274,000	10,181,500
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	4,159,000	4,446,400	4,159,000	4,446,400
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	2,853,800	2,748,000	2,853,800	2,748,000
Gross Premiums or Assessments	99,800	98,400	300,300	300,700
Interest Expense	$ 35,000	$ 35,400	$ 104,700	$ 106,100
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	4.54%	4.57%	4.54%	4.57%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.17%	5.88%	5.17%	5.88%