DERIVATIVE FINANCIAL INSTRUMENTS - Gain (Loss) (Details) - Derivatives not designated as Hedging Instruments - Fair Value Hedges - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ (13)	$ 36	$ 30	$ 80
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	13	13	43	34
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	(34)	9	(44)	9
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	41	37
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	(5)	3	(9)	4
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	2	0	4	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	$ (3)	$ (2)	$ (5)	$ (6)