DERIVATIVES - Effect of Derivative Instruments on Net Income and Stockholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net gains (losses) recognized in OCI	$ (66)	$ 130	$ 138
Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net losses reclassified	183	184	(68)
Interest expense - long-term borrowed funds
Derivative Instruments, Gain (Loss) [Line Items]
Amount of pre-tax net losses reclassified	$ (48)	$ (35)	$ 11