DERIVATIVE FINANCIAL INSTRUMENTS - Gain (Loss) (Details) - Derivatives not designated as Hedging Instruments - Fair Value Hedges - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ 17	$ 8	$ 43	$ 44
Interest rate contracts \| Capital markets and advisory fees \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	18	13	30	21
Interest rate contracts \| Mortgage banking income \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	(18)	(21)	(10)	0
Foreign exchange contracts \| Capital markets and advisory fees \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	14	13	27	24
Equity contracts \| Other noninterest income and other noninterest expense \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	3	4	(4)	1
Commodities contracts \| Capital markets and advisory fees \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	1	1	2	2
Credit contracts \| Other noninterest income \| Location, Statement of Income, Balance [Axis]: us-gaap:NoninterestIncome
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ (1)	$ (2)	$ (2)	$ (4)