BANK DEPOSITS, Bank Deposits by Insured and Uninsured (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Deposits [Abstract]
FDIC-insured bank deposits	$ 48,268	$ 48,344
Bank deposits exceeding FDIC insurance limit	6,575	5,855
Total bank deposits	$ 54,843	$ 54,199
FDIC-insured bank deposits as a % of total bank deposits	88.00%	89.00%
Related Party Transaction [Line Items]
Bank deposits exceeding FDIC insurance limit	$ 6,575	$ 5,855
Related party
Deposits [Abstract]
Bank deposits exceeding FDIC insurance limit	888	764
Related Party Transaction [Line Items]
Bank deposits exceeding FDIC insurance limit	$ 888	$ 764