BORROWED FUNDS - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Principal balance	$ 12,600	$ 12,500
Unamortized deferred issuance costs and/or discounts	78	85
Hedging basis adjustments	(4)	(8)
Short-term borrowed funds	249	0
Available borrowing capacity	75,700
Federal Home Loan Bank Advances and Letters of Credit | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds	6,300	4,600
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Available borrowing capacity	$ 21,900	$ 21,100