BANK DEPOSITS, Bank Deposits by Insured and Uninsured (Details) - USD ($) $ in Millions	Dec. 31, 2025	Sep. 30, 2025
Deposits [Abstract]
FDIC-insured bank deposits	$ 50,001	$ 49,117
Bank deposits exceeding FDIC insurance limit	10,151	9,780
Total bank deposits	$ 60,152	$ 58,897
FDIC-insured bank deposits as a % of total bank deposits	83.00%	83.00%
Related Party Transaction [Line Items]
Bank deposits exceeding FDIC insurance limit	$ 10,151	$ 9,780
Related party
Deposits [Abstract]
Bank deposits exceeding FDIC insurance limit	1,450	1,240
Related Party Transaction [Line Items]
Bank deposits exceeding FDIC insurance limit	$ 1,450	$ 1,240