SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Net revenues:
Total revenues	$ 3,013	$ 2,786
Pre-tax income/(loss):
Total pre-tax income	630	652
Total assets:
Total assets	80,130		$ 78,360
Goodwill and Intangible Assets:
Goodwill	1,444		1,437
U.S.
Net revenues:
Total revenues	2,761	2,540
Pre-tax income/(loss):
Total pre-tax income	605	609
Total assets:
Total assets	74,319		72,506
Goodwill and Intangible Assets:
Goodwill	1,250		1,250
Canada
Net revenues:
Total revenues	139	134
Pre-tax income/(loss):
Total pre-tax income	27	31
Total assets:
Total assets	3,382		3,404
Goodwill and Intangible Assets:
Goodwill	25		25
Europe
Net revenues:
Total revenues	113	112
Pre-tax income/(loss):
Total pre-tax income	(2)	$ 12
Total assets:
Total assets	2,429		2,450
Goodwill and Intangible Assets:
Goodwill	$ 169		$ 162