Insurance Liabilities (Future Policy Benefits - Reconciliation) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 31,655	$ 32,387
Liabilities reported in the preceding rollforward tables
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	22,531	22,005
Long-term care insurance (1)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	5,285	5,514
ULSG liabilities, including liability for profits followed by losses (2)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	44	1,202
Effect of changes in assumptions for ULSG liabilities, including the liability for profits followed by losses	(1,200)
Participating whole life insurance (3)
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	3,033	2,923
Deferred profit liabilities
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	437	431
Other
Liability for Future Policy Benefit, by Product Segment [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 325	$ 312