BUSINESS OPERATING SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net interest income	$ 4,512	$ 4,586	$ 4,614
Noninterest income	2,135	2,319	1,877
Total revenue	6,647	6,905	6,491
Noninterest expense	4,081	3,991	3,847
Profit (loss) before provision for credit losses	2,566	2,914	2,644
Provision for credit losses	(411)	1,616	393
Income before income tax expense	2,977	1,298	2,251
Income tax expense	658	241	460
NET INCOME	2,319	1,057	1,791
Total average assets	185,106	176,442	162,176
Operating Segments
Segment Reporting Information [Line Items]
Noninterest income	2,135	2,319	1,877
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	3,562	3,311	3,182
Noninterest income	1,223	1,655	1,156
Total revenue	4,785	4,966	4,338
Noninterest expense	2,987	2,964	2,851
Profit (loss) before provision for credit losses	1,798	2,002	1,487
Provision for credit losses	185	288	325
Income before income tax expense	1,613	1,714	1,162
Income tax expense	410	429	287
NET INCOME	1,203	1,285	875
Total average assets	75,509	72,022	66,240
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	1,706	1,643	1,466
Noninterest income	809	595	607
Total revenue	2,515	2,238	2,073
Noninterest expense	973	860	858
Profit (loss) before provision for credit losses	1,542	1,378	1,215
Provision for credit losses	156	398	97
Income before income tax expense	1,386	980	1,118
Income tax expense	300	206	248
NET INCOME	1,086	774	870
Total average assets	57,617	60,839	55,947
Other
Segment Reporting Information [Line Items]
Net interest income	(756)	(368)	(34)
Total revenue	(653)	(299)	80
Noninterest expense	121	167	138
Profit (loss) before provision for credit losses	(774)	(466)	(58)
Provision for credit losses	(752)	930	(29)
Income before income tax expense	(22)	(1,396)	(29)
Income tax expense	(52)	(394)	(75)
NET INCOME	30	(1,002)	46
Total average assets	$ 51,980	$ 43,581	$ 39,989