LOANS TO FINANCIAL ADVISORS, NET (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Sep. 30, 2025
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	$ 1,805	$ 1,658
No longer affiliated with the firm as of year-end	8	7
Total loans to financial advisors	1,813	1,665
Allowance for credit losses	(43)	(39)
Loans, net	1,770	1,626
Accrued interest receivable on loans to financial advisors (included in “Other receivables, net”)	$ 13	$ 12
Allowance for credit losses as a percent of total loans to financial advisors	2.37%	2.34%