COLLATERALIZED AGREEMENTS AND FINANCINGS, Schedule of Offsetting Transactions (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Reverse repurchase agreements
Gross amounts of recognized assets/liabilities	$ 193	$ 343
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	193	343
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(193)	(343)
Net amounts	0	0
Securities borrowed
Gross amounts of recognized assets/liabilities	300	248
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	300	248
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(293)	(243)
Net amounts	7	5
Repurchase agreements
Gross amounts of recognized assets/liabilities	228	150
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	228	150
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(228)	(150)
Net amounts	0	0
Securities loaned
Gross amounts of recognized assets/liabilities	88	323
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	88	323
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(78)	(311)
Net amounts	$ 10	$ 12