Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Key Assumptions used in Calculating the Reserve for Future Policy Benefits (Details)	Sep. 30, 2023	Sep. 30, 2022
Accident and health insurance
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average duration (in years)	4 years 3 months 18 days	3 years 8 months 12 days
Interest accretion rate (discount rate at contract issuance)	4.73%	4.69%
Current discount rate (upper-medium grade fixed income yield)	5.28%	4.73%
Traditional life
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average duration (in years)	14 years 9 months 18 days	13 years 4 months 24 days
Interest accretion rate (discount rate at contract issuance)	5.43%	5.60%
Current discount rate (upper-medium grade fixed income yield)	5.56%	5.38%