BUSINESS OPERATING SEGMENTS - Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 1,665	$ 1,145	$ 4,317	$ 3,386
Noninterest income	512	514	1,504	1,541
Total revenue	2,177	1,659	5,821	4,927
Noninterest expense	1,241	1,011	3,652	3,020
Profit (loss) before provision (benefit) for credit losses	936	648	2,169	1,907
Provision (benefit) for credit losses	123	(33)	342	(386)
Income before income tax expense	813	681	1,827	2,293
Income tax expense (benefit)	177	151	407	504
NET INCOME	636	530	1,420	1,789
Total average assets	225,473	186,108	211,722	184,391
Operating Segments
Segment Reporting Information [Line Items]
Noninterest income	512	514	1,504	1,541
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,085	919	2,937	2,679
Noninterest income	270	315	807	949
Total revenue	1,355	1,234	3,744	3,628
Noninterest expense	863	749	2,528	2,250
Profit (loss) before provision (benefit) for credit losses	492	485	1,216	1,378
Provision (benefit) for credit losses	62	35	150	139
Income before income tax expense	430	450	1,066	1,239
Income tax expense (benefit)	111	114	273	315
NET INCOME	319	336	793	924
Total average assets	89,560	75,070	85,375	75,317
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	559	428	1,509	1,268
Noninterest income	213	168	647	516
Total revenue	772	596	2,156	1,784
Noninterest expense	325	226	905	679
Profit (loss) before provision (benefit) for credit losses	447	370	1,251	1,105
Provision (benefit) for credit losses	12	15	34	150
Income before income tax expense	435	355	1,217	955
Income tax expense (benefit)	101	81	271	205
NET INCOME	334	274	946	750
Total average assets	80,067	56,702	73,344	57,318
Other
Segment Reporting Information [Line Items]
Net interest income	21	(202)	(129)	(561)
Noninterest income	29	31	50	76
Total revenue	50	(171)	(79)	(485)
Noninterest expense	53	36	219	91
Profit (loss) before provision (benefit) for credit losses	(3)	(207)	(298)	(576)
Provision (benefit) for credit losses	49	(83)	158	(675)
Income before income tax expense	(52)	(124)	(456)	99
Income tax expense (benefit)	(35)	(44)	(137)	(16)
NET INCOME	(17)	(80)	(319)	115
Total average assets	$ 55,846	$ 54,336	$ 53,003	$ 51,756