BANK LOANS, NET, Held for Sale and Held for Investment (Details) $ in Millions	Sep. 30, 2024 USD ($) portfolio_segment	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Receivables [Abstract]
Number of loan portfolio segments | portfolio_segment	6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on bank loans, location	Other Receivables	Other Receivables
Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 46,451	$ 44,249
Allowance for loan losses	(457)	(474)
Loans, net	$ 45,994	$ 43,775
ACL as a % of total loans held for investment	0.99%	1.07%
Accrued interest receivable on bank loans (included in “Other receivables, net”)	$ 214	$ 200
Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	46,267	44,104
Allowance for loan losses	(457)	(474)	$ (396)	$ (320)
Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	46,267	44,104
Held for sale loans | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	184	145
SBL
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	16,233	14,606
SBL | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	16,233	14,606
Allowance for loan losses	(6)	(7)	(3)	(4)
SBL | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	16,233	14,606
C&I loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,953	10,406
C&I loans | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,953	10,406
Allowance for loan losses	(173)	(214)	(226)	(191)
C&I loans | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,953	10,406
CRE loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	7,615	7,221
CRE loans | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	7,615	7,221
Allowance for loan losses	(188)	(161)	(87)	(66)
CRE loans | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	7,615	7,221
REIT loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,716	1,668
REIT loans | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,716	1,668
Allowance for loan losses	(23)	(16)	(21)	(22)
REIT loans | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,716	1,668
Residential mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,412	8,662
Residential mortgage loans | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,412	8,662
Allowance for loan losses	(65)	(74)	(57)	(35)
Residential mortgage loans | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	9,412	8,662
Tax-exempt loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,338	1,541
Tax-exempt loans | Total loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	1,338	1,541
Allowance for loan losses	(2)	(2)	$ (2)	$ (2)
Tax-exempt loans | Total loans held for investment | Nonrelated party
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for investment	$ 1,338	$ 1,541