BORROWED FUNDS - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Principal balance	$ 14,000	$ 13,600
Unamortized deferred issuance costs and/or discounts	90	74
Hedging basis adjustments	(8)	(17)
Short-term borrowed funds	15	505
Available borrowing capacity	72,300
Federal Home Loan Bank Advances and Letters of Credit | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds	5,500	9,200
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Available borrowing capacity	$ 20,400	$ 15,900