BANK DEPOSITS, Summary of Bank Deposits (Details) - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Bank deposits:
Savings and money market accounts	$ 33,574	$ 31,415
Certificates of deposit	701	878
NOW accounts	371	164
Demand deposits (non-interest-bearing)	39	38
Total bank deposits	$ 34,685	$ 32,495
Weighted-average rate [Abstract]
Savings and money market accounts, weighted-average rate (in hundredths)	0.01%	0.01%
Certificates of deposit, weighted-average rate (in hundredths)	1.83%	1.87%
NOW accounts, weighted-average rate (in hundredths)	1.00%	1.84%
Demand deposits (non-interest-bearing), weighted-average rate (in hundredths)	0.00%	0.00%
Total bank deposits, weighted-average rate (in hundredths)	0.06%	0.07%
Related Party Transaction [Line Items]
Related party deposit liabilities	$ 409	$ 301
Time deposit amount that exceeds FDIC insurance limit	43
Raymond James Financial Inc
Related Party Transaction [Line Items]
Related party deposit liabilities	255
Raymond James Trust Company of New Hampshire
Related Party Transaction [Line Items]
Related party deposit liabilities	89
Raymond James Capital Services
Related Party Transaction [Line Items]
Related party deposit liabilities	$ 65