Long-Duration Insurance Contracts - Discount Rates for LFPB (Details)	Sep. 30, 2024	Sep. 30, 2023
Whole Life Insurance | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	4.20%	5.50%
Whole Life Insurance | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.90%	4.90%
Current discount rate	5.10%	5.90%
Term Life Insurance | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.20%	4.20%
Current discount rate	4.80%	5.90%
Term Life Insurance | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.20%	4.30%
Current discount rate	4.90%	5.90%
Experience Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	6.10%	6.10%
Current discount rate	5.00%	5.90%
Limited Pay Whole Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.00%	3.90%
Current discount rate	5.20%	5.90%
Supplemental health | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	5.20%	5.90%
Supplemental health | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	2.70%	2.70%
Current discount rate	5.00%	6.10%
Life Contingent SPIA Retirement Insurance | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	4.80%	5.80%
Life Contingent SPIA Retirement Insurance | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.10%	4.10%
Current discount rate	4.80%	5.80%