BANK LOANS, NET, Held for Sale and Held for Investment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	$ 44,098		$ 44,098			$ 43,635
Allowance for credit losses	(415)		(415)			(396)
Bank loans, net	$ 43,683		$ 43,683			$ 43,239
ACL as a % of total loans held for investment	0.94%		0.94%			0.91%
Accrued interest receivable on bank loans (included in “Other receivables, net”)	$ 192		$ 192			$ 137
Net unamortized discounts, unearned income, and deferred loan fees and costs	89		89			112
C&I loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	11,259		11,259			11,173
CRE loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	7,054		7,054			6,549
REIT loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	1,717		1,717			1,592
Tax-exempt loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	1,643		1,643			1,501
Residential mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	8,079		8,079			7,386
SBL
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	14,227		14,227			15,297
Loans held for investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	43,979		43,979			43,498
Allowance for credit losses	(415)	$ (328)	(415)	$ (328)	$ (408)	(396)	$ (308)	$ (320)
Loans held for investment | C&I loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	11,259		11,259			11,173
Allowance for credit losses	(219)	(195)	(219)	(195)	(222)	(226)	(179)	(191)
Loans held for investment | CRE loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	7,054		7,054			6,549
Allowance for credit losses	(100)	(71)	(100)	(71)	(91)	(87)	(72)	(66)
Loans held for investment | REIT loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	1,717		1,717			1,592
Allowance for credit losses	(15)	(25)	(15)	(25)	(15)	(21)	(22)	(22)
Loans held for investment | Tax-exempt loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	1,643		1,643			1,501
Allowance for credit losses	(2)	(2)	(2)	(2)	(2)	(2)	(2)	(2)
Loans held for investment | Residential mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	8,079		8,079			7,386
Allowance for credit losses	(74)	(32)	(74)	(32)	$ (74)	(57)	$ (30)	$ (35)
Loans held for investment | SBL
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	14,227		14,227			15,297
Allowance for credit losses	(5)		(5)
Loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable past due	119		119			$ 137
Loans held for sale originated or purchased	$ 624	$ 999	$ 1,430	$ 1,970