COLLATERALIZED AGREEMENTS AND FINANCINGS, Schedule of Offsetting Transactions (Details) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020
Reverse repurchase agreements
Gross amounts of recognized assets/liabilities	$ 162	$ 207
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	162	207
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(162)	(207)
Net amounts	0	0
Securities borrowed
Gross amounts of recognized assets/liabilities	371	215
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	371	215
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(355)	(209)
Net amounts	16	6
Gross amounts of recognized assets/liabilities	533	422
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	533	422
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(517)	(416)
Net amounts	16	6
Repurchase agreements
Gross amounts of recognized assets/liabilities	233	165
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	233	165
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(233)	(165)
Net amounts	0	0
Securities loaned
Gross amounts of recognized assets/liabilities	64	85
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	64	85
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(58)	(79)
Net amounts	6	6
Gross amounts of recognized assets/liabilities	297	250
Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	0	0
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	297	250
Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition	(291)	(244)
Net amounts	$ 6	$ 6