SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023
Net revenues:
Total revenues	$ 3,228	$ 2,907	$ 9,359	$ 8,566
Pre-tax income/(loss):
Total pre-tax income	644	486	1,883	1,695
Total assets:
Total assets	80,628		80,628		$ 78,360
Goodwill and Intangible Assets:
Goodwill	1,442		1,442		1,437
U.S.
Net revenues:
Total revenues	2,950	2,652	8,557	7,819
Pre-tax income/(loss):
Total pre-tax income	615	492	1,801	1,625
Total assets:
Total assets	74,881		74,881		72,506
Goodwill and Intangible Assets:
Goodwill	1,250		1,250		1,250
Canada
Net revenues:
Total revenues	154	140	448	418
Pre-tax income/(loss):
Total pre-tax income	31	17	95	84
Total assets:
Total assets	3,274		3,274		3,404
Goodwill and Intangible Assets:
Goodwill	24		24		25
Europe
Net revenues:
Total revenues	124	115	354	329
Pre-tax income/(loss):
Total pre-tax income	(2)	$ (23)	(13)	$ (14)
Total assets:
Total assets	2,473		2,473		2,450
Goodwill and Intangible Assets:
Goodwill	$ 168		$ 168		$ 162