DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Derivative Assets and Liability Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Derivative assets
Derivative assets	$ 605	$ 465
Counterparty netting	(41)	(24)
Cash collateral netting	(112)	(103)
Total amounts offset	(153)	(127)
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	452	338
Financial instruments	(373)	(297)
Net amount	79	41
Notional amount	20,456	15,537
Derivative liabilities
Derivative liabilities	535	434
Counterparty netting	(41)	(24)
Cash collateral netting	(100)	(97)
Total amounts offset	(141)	(121)
Net amounts presented on the Condensed Consolidated Statements of Financial Condition	394	313
Financial instruments	(351)	(280)
Net amount	43	33
Derivatives not designated as hedging instruments
Derivative assets
Derivative assets	605	464
Notional amount	18,764	13,831
Derivative liabilities
Derivative liabilities	528	433
Derivatives not designated as hedging instruments | Interest rate - matched book
Derivative assets
Interest rate - matched book	351	280
Notional amount	2,182	2,296
Derivative liabilities
Interest rate - matched book	351	280
Derivatives not designated as hedging instruments | Interest rate - other
Derivative assets
Derivative assets	254	184
Notional amount	15,443	10,690
Derivative liabilities
Derivative liabilities	171	146
Derivatives not designated as hedging instruments | Foreign exchange
Derivative assets
Derivative assets	0	0
Notional amount	623	573
Derivative liabilities
Derivative liabilities	5	1
Derivatives not designated as hedging instruments | Other
Derivative assets
Derivative assets	0	0
Notional amount	516	272
Derivative liabilities
Derivative liabilities	1	6
Derivatives designated as hedging instruments
Derivative assets
Derivative assets	0	1
Notional amount	1,692	1,706
Derivative liabilities
Derivative liabilities	7	1
Derivatives designated as hedging instruments | Interest rate
Derivative assets
Derivative assets	0	1
Notional amount	850	850
Derivative liabilities
Derivative liabilities	0	0
Derivatives designated as hedging instruments | Foreign exchange
Derivative assets
Derivative assets	0	0
Notional amount	842	856
Derivative liabilities
Derivative liabilities	$ 7	$ 1