DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Derivative Asset and Liability Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023
Derivative assets
Derivative assets	$ 383	$ 526
Counterparty netting	(57)	(29)
Cash collateral netting	(131)	(232)
Total amounts offset	(188)	(261)
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	195	265
Financial instruments	(81)	(131)
Net amount	114	134
Derivative liabilities
Derivative liabilities	424	578
Counterparty netting	(57)	(29)
Cash collateral netting	(57)	(59)
Total amounts offset	(114)	(88)
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	310	490
Financial instruments	0	0
Net amount	310	490
Notional amount	22,514	22,441
Derivatives not designated as hedging instruments
Derivative assets
Derivative assets	377	513
Derivative liabilities
Derivative liabilities	416	578
Notional amount	20,081	20,069
Derivatives not designated as hedging instruments | Interest rate
Derivative assets
Derivative assets	377	509
Derivative liabilities
Derivative liabilities	409	576
Notional amount	17,861	18,270
Derivatives not designated as hedging instruments | Foreign exchange
Derivative assets
Derivative assets	0	4
Derivative liabilities
Derivative liabilities	7	2
Notional amount	1,183	1,191
Derivatives not designated as hedging instruments | Other
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Notional amount	1,037	608
Derivatives designated as hedging instruments
Derivative assets
Derivative assets	6	13
Derivative liabilities
Derivative liabilities	8	0
Notional amount	2,433	2,372
Derivatives designated as hedging instruments | Interest rate
Derivative assets
Derivative assets	6	8
Derivative liabilities
Derivative liabilities	0	0
Notional amount	1,225	1,200
Derivatives designated as hedging instruments | Foreign exchange
Derivative assets
Derivative assets	0	5
Derivative liabilities
Derivative liabilities	8	0
Notional amount	$ 1,208	$ 1,172