GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS, NET, Net Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	$ 134	$ 147
Additions	109
Amortization expense	(21)	(13)
Net identifiable intangible assets as of end of year	222	134
Private Client Group
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	31	35
Additions	96
Amortization expense	(7)	(4)
Net identifiable intangible assets as of end of year	120	31
Capital Markets
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	13	17
Additions	13
Amortization expense	(9)	(4)
Net identifiable intangible assets as of end of year	17	13
Asset Management
Finite-lived Intangible Assets [Roll Forward]
Net identifiable intangible assets as of beginning of year	90	95
Additions	0
Amortization expense	(5)	(5)
Net identifiable intangible assets as of end of year	$ 85	$ 90