SEGMENT INFORMATION, Information Concerning Operations (Details) $ in Millions	3 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Sep. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	5
Net revenues:
Total net revenues	$ 3,013	$ 2,786
Pre-tax income/(loss):
Total pre-tax income	630	652
Net interest income (expense):
Net interest income	546	586
Total assets:
Total assets	80,130		$ 78,360
Goodwill and Intangible Assets:
Goodwill	1,444		1,437
Operating segments | Private Client Group
Net revenues:
Total net revenues	2,226	2,063
Pre-tax income/(loss):
Total pre-tax income	439	434
Net interest income (expense):
Net interest income	92	87
Total assets:
Total assets	12,744		12,375
Goodwill and Intangible Assets:
Goodwill	571		564
Operating segments | Capital Markets
Net revenues:
Total net revenues	338	295
Pre-tax income/(loss):
Total pre-tax income	3	(16)
Net interest income (expense):
Net interest income	1	0
Total assets:
Total assets	2,732		3,087
Goodwill and Intangible Assets:
Goodwill	275		275
Operating segments | Asset Management
Net revenues:
Total net revenues	235	207
Pre-tax income/(loss):
Total pre-tax income	93	80
Net interest income (expense):
Net interest income	3	2
Total assets:
Total assets	569		567
Goodwill and Intangible Assets:
Goodwill	69		529
Operating segments | Bank
Net revenues:
Total net revenues	441	508
Pre-tax income/(loss):
Total pre-tax income	92	136
Net interest income (expense):
Net interest income	426	491
Total assets:
Total assets	61,517		60,041
Goodwill and Intangible Assets:
Goodwill	529		69
Operating segments | Other
Net revenues:
Total net revenues	26	9
Pre-tax income/(loss):
Total pre-tax income	3	18
Net interest income (expense):
Net interest income	24	6
Total assets:
Total assets	2,568		$ 2,290
Intersegment eliminations
Net revenues:
Total net revenues	$ (253)	$ (296)