GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS, NET, Net Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	$ 509	$ 222
Additions	0	334
Amortization expense	(45)	(33)
Foreign currency translations	6	(14)
Net identifiable intangible assets as of end of year	470	509
Private Client Group
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	178	120
Additions	0	85
Amortization expense	(16)	(13)
Foreign currency translations	6	(14)
Net identifiable intangible assets as of end of year	168	178
Capital Markets
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	60	17
Additions	0	52
Amortization expense	(10)	(9)
Foreign currency translations	0	0
Net identifiable intangible assets as of end of year	50	60
Asset Management
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	139	85
Additions	0	61
Amortization expense	(7)	(7)
Foreign currency translations	0	0
Net identifiable intangible assets as of end of year	132	139
Bank
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	132	0
Additions	0	136
Amortization expense	(12)	(4)
Foreign currency translations	0	0
Net identifiable intangible assets as of end of year	$ 120	$ 132