Liability for Future Policyholder Benefits - Reconciliation of the Net Liability for Future Benefits to Life and Health Insurance Reserves and Other Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Weighted-Average Duration	13 years 10 months 24 days	15 years 3 months 18 days	14 years 7 months 6 days
Net Liability for Future Policyholder Benefits, post-flooring	$ 2,649.8	$ 2,937.8
Deferred Profit Liability	412.1	337.8	$ 253.6	$ 193.4
Other	137.8	146.8
Total Life and Health Insurance Reserves	3,199.7	3,422.4
Term Life Insurance
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Expected Future Benefit Payments, undiscounted	10,100.0	10,185.2
Expected Future Gross Premiums, undiscounted	3,976.4	4,107.9
Expected Future Gross Premiums, discounted	2,628.1	2,800.6
Gross Premiums or Assessments	399.6	399.0	392.1
Interest Expense	$ 139.5	$ 141.3	$ 142.1
Interest Accretion Rate	4.55%	4.57%
Current Discount Rate	5.77%	5.08%