Insurance Liabilities - Weighted-average interest rates (Details)	Sep. 30, 2023	Sep. 30, 2022
General Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	1.84%	1.70%
Weighted-average interest rate, current discount rate	3.92%	2.85%
Individual Retirement
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	3.75%	3.42%
Weighted-average interest rate, current discount rate	5.92%	5.52%
Group Retirement
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	5.15%	5.20%
Weighted-average interest rate, current discount rate	5.90%	5.50%
Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	4.14%	4.13%
Weighted-average interest rate, current discount rate	5.92%	5.56%
Life Insurance | Universal Life
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, current discount rate	3.94%	3.75%
Institutional Markets
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	3.97%	3.41%
Weighted-average interest rate, current discount rate	5.87%	5.56%
Other Operations before consolidation and eliminations
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, original discount rate	4.87%	4.89%
Weighted-average interest rate, current discount rate	5.94%	5.57%
Other Operations before consolidation and eliminations | Universal Life
Liability for Future Policy Benefit, Activity [Line Items]
Weighted-average interest rate, current discount rate	4.20%	4.20%