ACQUISITIONS, TriState Capital Narrative (Details) $ / shares in Units, shares in Thousands, $ in Millions		3 Months Ended		9 Months Ended
	Jun. 01, 2022 USD ($) $ / shares shares	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 15, 2021 USD ($)
Business Acquisition [Line Items]
Bank loan provision/(benefit) for credit losses		$ 56	$ (19)	$ 66	$ (37)
TriState Capital
Business Acquisition [Line Items]
Note receivable						$ 125
Note receivable interest rate, year one						2.25%
Series A Non-Cumulative Perpetual Preferred Stock
Business Acquisition [Line Items]
Preferred stock percentage	6.75%
Series A Non-Cumulative Perpetual Preferred Stock | TriState Capital
Business Acquisition [Line Items]
Preferred stock percentage	6.75%
Series B Non-Cumulative Perpetual Preferred Stock
Business Acquisition [Line Items]
Preferred stock percentage	6.375%
Series B Non-Cumulative Perpetual Preferred Stock | TriState Capital
Business Acquisition [Line Items]
Preferred stock percentage	6.375%
TriState Capital
Business Acquisition [Line Items]
Cash and stock consideration	$ 1,408
Restricted stock awards (in shares) | shares	551
Consideration transferred, note receivable	$ 123
Net revenues since acquisition date				29
Net income (loss) since acquisition date				$ (16)
Bank loan provision/(benefit) for credit losses	26
Lending commitments, provision for credit losses	5
Long-term debt assumed	11,700
TriState Capital | Initial provision for credit losses on non-PCD loans acquired with TriState Capital Bank
Business Acquisition [Line Items]
Long-term debt assumed	$ 11,360
TriState Capital | TriState Capital Common Stock
Business Acquisition [Line Items]
Share price (in dollars per share) | $ / shares	$ 6
Consideration transferred, share issuance ratio	0.25
TriState Capital | TriState Series C Convertible Preferred Stock
Business Acquisition [Line Items]
Share price (in dollars per share) | $ / shares	$ 30