COLLATERALIZED AGREEMENTS AND FINANCINGS, Schedule of Offsetting Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Reverse repurchase agreements
Gross amounts of recognized assets/liabilities	$ 449	$ 187
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	449	187
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(449)	(187)
Net amounts	0	0
Securities borrowed
Gross amounts of recognized assets/liabilities	278	231
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	278	231
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(271)	(224)
Net amounts	7	7
Gross amounts of recognized assets/liabilities	727	418
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	727	418
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(720)	(411)
Net amounts	7	7
Repurchase agreements
Gross amounts of recognized assets/liabilities	371	157
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	371	157
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(371)	(157)
Net amounts	0	0
Securities loaned
Gross amounts of recognized assets/liabilities	584	180
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	584	180
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(565)	(173)
Net amounts	19	7
Gross amounts of recognized assets/liabilities	955	337
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts included in the Condensed Consolidated Statements of Financial Condition	955	337
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(936)	(330)
Net amounts	$ 19	$ 7