COLLATERALIZED AGREEMENTS AND FINANCINGS, Schedule of Offsetting Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Reverse repurchase agreements
Gross amounts of recognized assets/liabilities	$ 130	$ 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	130	343
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(130)	(343)
Net amounts	0	0
Securities borrowed
Gross amounts of recognized assets/liabilities	250	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	250	248
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(240)	(243)
Net amounts	10	5
Repurchase agreements
Gross amounts of recognized assets/liabilities	215	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	215	150
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(215)	(150)
Net amounts	0	0
Securities loaned
Gross amounts of recognized assets/liabilities	28	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	28	323
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(24)	(311)
Net amounts	$ 4	$ 12