BORROWED FUNDS - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Principal balance	$ 10,500	$ 12,500
Unamortized deferred issuance costs and/or discounts	75	85
Hedging basis adjustments	(1)	(8)
Short-term borrowed funds	214	0
Available borrowing capacity	78,000
Federal Home Loan Bank Advances and Letters of Credit | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds	4,900	4,600
Federal Home Loan Bank advances
Debt Instrument [Line Items]
Available borrowing capacity	$ 24,300	$ 21,100