Insurance Liabilities (Reconciliation of Policyholder Account Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 87,903	$ 86,836
Rollforwards Total
Policyholder Account Balance [Line Items]
Policyholder Account Balance	76,589	73,996
Funding agreements classified as investment contracts
Policyholder Account Balance [Line Items]
Policyholder Account Balance	9,876	11,561
Institutional group annuities
Policyholder Account Balance [Line Items]
Policyholder Account Balance	584	363
Other investment contract liabilities
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 854	$ 916