BANK LOANS, NET, Held for Investment Residential Mortgage Loan Portfolio by FICO Score and by LTV Ratio (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	$ 42,220	$ 25,314
Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	42,054	25,169
Residential mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	6,728	5,318
Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	6,728	5,318
Below 80% | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	5,258	4,123
80%+ | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	1,470	1,195
Below 600 | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	65	67
600 - 699 | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	463	416
700 - 799 | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	4,943	3,772
800 + | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	1,231	1,058
FICO score not available | Residential mortgage loans | Loans held for investment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable past due	$ 26	$ 5