LOANS TO FINANCIAL ADVISORS, NET (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Past due period	180 days
Related party
Financing Receivable, Allowance for Credit Loss [Line Items]
Affiliated with the firm as of year-end	$ 1,158	$ 1,173
No longer affiliated with the firm as of year-end	10	8
Loans, gross	1,168	1,181
Allowance for credit losses	(32)	(29)
Loans, net	1,136	1,152
Accrued interest receivable on bank loans (included in “Other receivables, net”)	$ 6	$ 5
ACL as a % of total loans held for investment	2.74%	2.46%