BORROWED FUNDS - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Principal balance	$ 14,200	$ 16,000
Unamortized deferred issuance costs and/or discounts	(80)	85
Hedging basis adjustments	(26)	(27)
Short-term borrowed funds	1,099	3
Available borrowing capacity	69,000
Federal Home Loan Bank Advances and Letters of Credit | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds	11,100	15,700
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Available borrowing capacity	$ 14,200	$ 11,500