SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Net revenues:
Total revenues	$ 12,821	$ 11,619	$ 11,003
Pre-tax income/(loss):
Total pre-tax income	2,643	2,280	2,022
Total assets:
Aggregate assets	82,992	78,360
Goodwill and Intangible Assets:
Goodwill	1,451	1,437	1,422
U.S.
Net revenues:
Total revenues	11,728	10,609	10,065
Pre-tax income/(loss):
Total pre-tax income	2,534	2,193	1,907
Total assets:
Aggregate assets	77,033	72,506
Goodwill and Intangible Assets:
Goodwill	1,250	1,250
Canada
Net revenues:
Total revenues	599	563	542
Pre-tax income/(loss):
Total pre-tax income	125	108	83
Total assets:
Aggregate assets	3,347	3,404
Goodwill and Intangible Assets:
Goodwill	25	25
Europe
Net revenues:
Total revenues	494	447	396
Pre-tax income/(loss):
Total pre-tax income	(16)	(21)	$ 32
Total assets:
Aggregate assets	2,612	2,450
Goodwill and Intangible Assets:
Goodwill	$ 176	$ 162