SEGMENT INFORMATION, Information Concerning Operations (Details) $ in Millions	12 Months Ended
	Sep. 30, 2024 USD ($) segment	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	5
Net revenues:
Net revenues	$ 12,821	$ 11,619	$ 11,003
Pre-tax income/(loss):
Total pre-tax income	2,643	2,280	2,022
Net interest income/(expense):
Net interest income	2,130	2,375	1,203
Total assets:
Aggregate assets	82,992	78,360
Goodwill and Intangible Assets:
Goodwill	1,451	1,437	1,422
Private Client Group
Goodwill and Intangible Assets:
Goodwill	578	564	550
Capital Markets
Goodwill and Intangible Assets:
Goodwill	275	275	274
Asset Management
Goodwill and Intangible Assets:
Goodwill	69	69	69
Bank
Goodwill and Intangible Assets:
Goodwill	529	529	529
Operating segments | Private Client Group
Net revenues:
Net revenues	9,459	8,654	7,710
Pre-tax income/(loss):
Total pre-tax income	1,785	1,763	1,030
Net interest income/(expense):
Net interest income	361	355	207
Total assets:
Aggregate assets	13,413	12,375
Operating segments | Capital Markets
Net revenues:
Net revenues	1,472	1,214	1,809
Pre-tax income/(loss):
Total pre-tax income	67	(91)	415
Net interest income/(expense):
Net interest income	6	3	9
Total assets:
Aggregate assets	3,518	3,087
Operating segments | Asset Management
Net revenues:
Net revenues	1,027	885	914
Pre-tax income/(loss):
Total pre-tax income	421	351	386
Net interest income/(expense):
Net interest income	14	10	2
Total assets:
Aggregate assets	616	567
Operating segments | Bank
Net revenues:
Net revenues	1,716	2,013	1,084
Pre-tax income/(loss):
Total pre-tax income	380	371	382
Net interest income/(expense):
Net interest income	1,656	1,957	1,053
Total assets:
Aggregate assets	62,367	60,041
Operating segments | Other
Net revenues:
Net revenues	99	59	(50)
Pre-tax income/(loss):
Total pre-tax income	(10)	(114)	(191)
Net interest income/(expense):
Net interest income	93	50	(68)
Total assets:
Aggregate assets	3,078	2,290
Intersegment eliminations
Net revenues:
Net revenues	$ (952)	$ (1,206)	$ (464)