Insurance (Reconciliation of Policyholder Account Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 77,474	$ 68,810
Rollforwards Total
Policyholder Account Balance [Line Items]
Policyholder Account Balance	65,452	57,762
Funding agreements classified as investment contracts
Policyholder Account Balance [Line Items]
Policyholder Account Balance	11,052	9,959
Other investment contract liabilities
Policyholder Account Balance [Line Items]
Policyholder Account Balance	$ 970	$ 1,089