GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS, NET, Schedule of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Roll Forward]
Goodwill as of beginning of year	$ 466	$ 464
Additions	193
Foreign currency translations	1	2
Goodwill as of end of year	660	466
Private Client Group
Goodwill [Roll Forward]
Goodwill as of beginning of year	277	275
Additions	139
Foreign currency translations	1	2
Goodwill as of end of year	417	277
Capital Markets
Goodwill [Roll Forward]
Goodwill as of beginning of year	120	120
Additions	54
Foreign currency translations	0	0
Goodwill as of end of year	174	120
Asset Management
Goodwill [Roll Forward]
Goodwill as of beginning of year	69	69
Additions	0
Foreign currency translations	0	0
Goodwill as of end of year	$ 69	$ 69