DERIVATIVE FINANCIAL INSTRUMENTS - Gain (Loss) (Details) - Derivatives not designated as Hedging Instruments - Fair Value Hedges - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ 26	$ 36
Interest rate contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	12	8
Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	8	21
Foreign exchange contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	13	11
Equity contracts | Other noninterest income and other noninterest expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	(7)	(3)
Commodities contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	1	1
Credit contracts | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ (1)	$ (2)