Long-Duration Insurance Contracts - Discount Rates for LFPB (Details)	Sep. 30, 2023	Sep. 30, 2022
Whole Life | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	5.50%	4.90%
Whole Life | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.90%	5.00%
Current discount rate	5.90%	5.40%
Term Life | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.20%	4.10%
Current discount rate	5.90%	5.50%
Term Life | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.30%	4.30%
Current discount rate	5.90%	5.50%
Experience Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	6.10%	6.10%
Current discount rate	5.90%	5.50%
Limited Pay Whole Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	3.90%	3.90%
Current discount rate	5.90%	5.40%
Supplemental health | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	5.90%	5.40%
Supplemental health | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	2.70%	2.70%
Current discount rate	6.10%	5.80%
SPIA (life contingent) | Minimum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	1.70%	1.70%
Current discount rate	5.80%	5.40%
SPIA (life contingent) | Maximum
Liability for Future Policy Benefit, by Product Segment [Line Items]
Interest accretion rate	4.10%	4.00%
Current discount rate	5.80%	5.40%