SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Net revenues:
Total revenues	$ 9,760	$ 7,990	$ 7,740
Pre-tax income/(loss):
Total pre-tax income	1,791	1,052	1,375
Loss on disposition of interests and sale of operations	0	7	15
Total assets:
Aggregate assets	61,891	47,482
Goodwill and Intangible Assets:
Goodwill	660	466	464
Goodwill additions	193
NWPS
Goodwill and Intangible Assets:
Goodwill additions	139
Financo
Goodwill and Intangible Assets:
Goodwill additions	30
Cebile
Goodwill and Intangible Assets:
Goodwill additions	24
Capital Markets
Pre-tax income/(loss):
Loss on disposition of interests and sale of operations		7	15
Goodwill and Intangible Assets:
Goodwill	174	120	120
Goodwill additions	54
U.S.
Net revenues:
Total revenues	9,067	7,446	7,211
Pre-tax income/(loss):
Total pre-tax income	1,701	1,028	1,356
Total assets:
Aggregate assets	57,952	44,090
Goodwill and Intangible Assets:
Goodwill	619	433
U.S. | Cebile
Goodwill and Intangible Assets:
Goodwill additions	17
Canada
Net revenues:
Total revenues	485	386	391
Pre-tax income/(loss):
Total pre-tax income	53	29	29
Total assets:
Aggregate assets	3,724	3,260
Goodwill and Intangible Assets:
Goodwill	25	24
Europe
Net revenues:
Total revenues	208	158	138
Pre-tax income/(loss):
Total pre-tax income	37	(5)	(10)
Total assets:
Aggregate assets	215	132
Goodwill and Intangible Assets:
Goodwill	16	9
Europe | Cebile
Goodwill and Intangible Assets:
Goodwill additions	$ 7
Europe | Capital Markets
Pre-tax income/(loss):
Loss on disposition of interests and sale of operations			$ 15
France | Capital Markets
Pre-tax income/(loss):
Loss on disposition of interests and sale of operations		$ 7