BUSINESS OPERATING SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 6,241	$ 6,012	$ 4,512
Noninterest income	1,983	2,009	2,135
Total revenue	8,224	8,021	6,647
Noninterest expense	5,507	4,892	4,081
Profit (loss) before provision for credit losses	2,717	3,129	2,566
Provision (benefit) for credit losses	687	474	(411)
Income before income tax expense	2,030	2,655	2,977
Income tax expense	422	582	658
NET INCOME	1,608	2,073	2,319
Total average assets	222,221	215,061	185,106
Operating Segments
Segment Reporting Information [Line Items]
Noninterest income	1,983	2,009	2,135
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	4,187	3,649	2,943
Noninterest income	1,067	1,063	1,223
Total revenue	5,254	4,712	4,166
Noninterest expense	3,542	3,255	2,857
Profit (loss) before provision for credit losses	1,712	1,457	1,309
Provision (benefit) for credit losses	280	174	162
Income before income tax expense	1,432	1,283	1,147
Income tax expense	373	328	292
NET INCOME	1,059	955	855
Total average assets	72,693	68,027	57,916
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	2,292	2,103	1,706
Noninterest income	784	845	809
Total revenue	3,076	2,948	2,515
Noninterest expense	1,295	1,223	973
Profit (loss) before provision for credit losses	1,781	1,725	1,542
Provision (benefit) for credit losses	250	46	156
Income before income tax expense	1,531	1,679	1,386
Income tax expense	378	375	300
NET INCOME	1,153	1,304	1,086
Total average assets	76,028	74,919	57,617
Operating Segments | Non-Core
Segment Reporting Information [Line Items]
Net interest income	(129)	378	594
Noninterest income	0	0	0
Total revenue	(129)	378	594
Noninterest expense	123	136	130
Profit (loss) before provision for credit losses	(252)	242	464
Provision (benefit) for credit losses	78	52	23
Income before income tax expense	(330)	190	441
Income tax expense	(86)	48	112
NET INCOME	(244)	142	329
Total average assets	13,745	18,121	17,592
Other
Segment Reporting Information [Line Items]
Net interest income	(109)	(118)	(731)
Noninterest income	132	101	103
Total revenue	23	(17)	(628)
Noninterest expense	547	278	121
Profit (loss) before provision for credit losses	(524)	(295)	(749)
Provision (benefit) for credit losses	79	202	(752)
Income before income tax expense	(603)	(497)	3
Income tax expense	(243)	(169)	(46)
NET INCOME	(360)	(328)	49
Total average assets	$ 59,755	$ 53,994	$ 51,981