SEGMENT INFORMATION, Information Concerning Operations (Details) $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($) businessSegment	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | businessSegment	5
Net revenues:
Net revenues	$ 11,619	$ 11,003	$ 9,760
Pre-tax income/(loss):
Total pre-tax income	2,280	2,022	1,791
Net interest income/(expense):
Net interest income	2,375	1,203	673
Total assets:
Aggregate assets	78,360	80,951
Goodwill and Intangible Assets:
Goodwill	1,437	1,422	660
Private Client Group
Goodwill and Intangible Assets:
Goodwill	564	550	417
Capital Markets
Goodwill and Intangible Assets:
Goodwill	275	274	174
Asset Management
Goodwill and Intangible Assets:
Goodwill	69	69	69
Bank
Goodwill and Intangible Assets:
Goodwill	529	529	0
Operating segments | Private Client Group
Net revenues:
Net revenues	8,654	7,710	6,611
Pre-tax income/(loss):
Total pre-tax income	1,763	1,030	749
Net interest income/(expense):
Net interest income	355	207	113
Total assets:
Aggregate assets	12,375	17,770
Operating segments | Capital Markets
Net revenues:
Net revenues	1,214	1,809	1,885
Pre-tax income/(loss):
Total pre-tax income	(91)	415	532
Net interest income/(expense):
Net interest income	3	9	6
Total assets:
Aggregate assets	3,087	3,951
Operating segments | Asset Management
Net revenues:
Net revenues	885	914	867
Pre-tax income/(loss):
Total pre-tax income	351	386	389
Net interest income/(expense):
Net interest income	10	2	0
Total assets:
Aggregate assets	567	556
Operating segments | Bank
Net revenues:
Net revenues	2,013	1,084	672
Pre-tax income/(loss):
Total pre-tax income	371	382	367
Net interest income/(expense):
Net interest income	1,957	1,053	642
Total assets:
Aggregate assets	60,041	56,737
Operating segments | Other
Net revenues:
Net revenues	59	(50)	(8)
Pre-tax income/(loss):
Total pre-tax income	(114)	(191)	(246)
Net interest income/(expense):
Net interest income	50	(68)	(88)
Total assets:
Aggregate assets	2,290	1,937
Intersegment eliminations
Net revenues:
Net revenues	$ (1,206)	$ (464)	$ (267)