DERIVATIVE FINANCIAL INSTRUMENTS - Gain (Loss) (Details) - Derivatives not designated as Hedging Instruments - Fair Value Hedges - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	$ 84	$ 5	$ 31
Interest rate contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	49	37	30
Interest rate contracts | Mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	0	(49)	(10)
Interest rate swaptions | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	0	0	(24)
Foreign exchange contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	50	45	45
Equity contracts | Other noninterest income and other noninterest expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	(11)	(18)	(13)
Commodities contracts | Capital markets and advisory fees
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	3	4	5
Credit contracts | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	$ (7)	$ (14)	$ (2)