Other Insurance Liabilities and Separate Accounts - Weighted-average Interest Rates and Durations (Details)	Sep. 30, 2023	Sep. 30, 2022
Large Case Pensions
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	4.20%	4.20%
Current discount rate	5.86%	5.42%
Weighted-average duration of long-duration insurance liabilities	7 years 4 months 24 days	7 years 4 months 24 days
Long-Term Care
Liability for Future Policy Benefit, Activity [Line Items]
Interest accretion rate	5.11%	5.11%
Current discount rate	5.99%	5.65%
Weighted-average duration of long-duration insurance liabilities	12 years 2 months 12 days	12 years 9 months 18 days