SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Sep. 30, 2024
Net revenues:
Total revenues	$ 3,398	$ 3,228	$ 10,338	$ 9,359
Pre-tax income/(loss):
Total pre-tax income	563	644	1,983	1,883
Total assets:
Total assets	84,815		84,815		$ 82,992
Goodwill and Intangible Assets:
Goodwill	1,455		1,455		1,451
U.S.
Net revenues:
Total revenues	3,107	2,950	9,445	8,557
Pre-tax income/(loss):
Total pre-tax income	546	615	1,875	1,801
Total assets:
Total assets	78,714		78,714		77,033
Goodwill and Intangible Assets:
Goodwill	1,250		1,250		1,250
Canada
Net revenues:
Total revenues	149	154	474	448
Pre-tax income/(loss):
Total pre-tax income	23	31	97	95
Total assets:
Total assets	3,185		3,185		3,347
Goodwill and Intangible Assets:
Goodwill	24		24		25
Europe
Net revenues:
Total revenues	142	124	419	354
Pre-tax income/(loss):
Total pre-tax income	(6)	$ (2)	11	$ (13)
Total assets:
Total assets	2,916		2,916		2,612
Goodwill and Intangible Assets:
Goodwill	$ 181		$ 181		$ 176