SEGMENT INFORMATION, Information Concerning Operations (Details) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2023 USD ($) businessSegment	Mar. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | businessSegment			5
Revenues:
Total net revenues	$ 2,873	$ 2,673	$ 5,659	$ 5,454
Pre-tax income
Total pre-tax income	557	433	1,209	991
Insurance settlement			32
Net interest income (expense):
Net interest income	631	204	1,217	392
Total assets:
Total assets	79,180		79,180		$ 80,951
Goodwill:
Goodwill	1,438		1,438		1,422
Operating segments | Private Client Group
Revenues:
Total net revenues	2,144	1,922	4,207	3,761
Pre-tax income
Total pre-tax income	441	213	875	408
Net interest income (expense):
Net interest income	88	34	175	64
Total assets:
Total assets	13,035		13,035		17,770
Goodwill:
Goodwill	565		565		550
Operating segments | Capital Markets
Revenues:
Total net revenues	302	413	597	1,027
Pre-tax income
Total pre-tax income	(34)	87	(50)	288
Net interest income (expense):
Net interest income	1	2	1	5
Total assets:
Total assets	2,920		2,920		3,951
Goodwill:
Goodwill	275		275		274
Operating segments | Asset Management
Revenues:
Total net revenues	216	234	423	470
Pre-tax income
Total pre-tax income	82	103	162	210
Net interest income (expense):
Net interest income	3	0	5	0
Total assets:
Total assets	521		521		556
Goodwill:
Goodwill	69		69		69
Operating segments | Bank
Revenues:
Total net revenues	540	197	1,048	380
Pre-tax income
Total pre-tax income	91	83	227	185
Net interest income (expense):
Net interest income	530	189	1,021	366
Total assets:
Total assets	60,400		60,400		56,737
Goodwill:
Goodwill	529		529		529
Operating segments | Other
Revenues:
Total net revenues	10	(18)	19	(33)
Pre-tax income
Total pre-tax income	(23)	(53)	(5)	(100)
Net interest income (expense):
Net interest income	9	(21)	15	(43)
Total assets:
Total assets	2,304		2,304		$ 1,937
Intersegment eliminations
Revenues:
Total net revenues	$ (339)	$ (75)	$ (635)	$ (151)