DERIVATIVES - Effect of Derivative Instruments on Net Income and Stockholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax net gains (losses) recognized in OCI	$ 341	$ (725)	$ (145)
Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net losses reclassified from AOCI	(751)	(945)	(596)
Noninterest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net losses reclassified from AOCI	(9)	0	0
Interest Expense Long-Term Borrowed Funds
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net losses reclassified from AOCI	$ (1)	$ (1)	$ 0