BUSINESS OPERATING SEGMENTS - Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Net interest income	$ 1,505	$ 1,124	$ 2,652	$ 2,241
Noninterest income	494	485	992	1,027
Total revenue	1,999	1,609	3,644	3,268
Noninterest expense	1,305	991	2,411	2,009
Profit (loss) before provision (benefit) for credit losses	694	618	1,233	1,259
Provision (benefit) for credit losses	216	(213)	219	(353)
Income before income tax expense	478	831	1,014	1,612
Income tax expense (benefit)	114	183	230	353
NET INCOME	364	648	784	1,259
Total average assets	220,967	184,456	204,732	183,518
Operating Segments
Segment Reporting Information [Line Items]
Noninterest income	494	485	992	1,027
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	995	897	1,852	1,760
Noninterest income	280	283	537	634
Total revenue	1,275	1,180	2,389	2,394
Noninterest expense	881	751	1,665	1,501
Profit (loss) before provision (benefit) for credit losses	394	429	724	893
Provision (benefit) for credit losses	39	45	88	104
Income before income tax expense	355	384	636	789
Income tax expense (benefit)	90	98	162	201
NET INCOME	265	286	474	588
Total average assets	88,881	75,600	83,247	75,443
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	534	419	950	840
Noninterest income	221	178	434	348
Total revenue	755	597	1,384	1,188
Noninterest expense	308	226	580	453
Profit (loss) before provision (benefit) for credit losses	447	371	804	735
Provision (benefit) for credit losses	10	34	22	135
Income before income tax expense	437	337	782	600
Income tax expense (benefit)	96	72	170	124
NET INCOME	341	265	612	476
Total average assets	78,638	57,527	69,927	57,632
Other
Segment Reporting Information [Line Items]
Net interest income	(24)	(192)	(150)	(359)
Noninterest income	(7)	24	21	45
Total revenue	(31)	(168)	(129)	(314)
Noninterest expense	116	14	166	55
Profit (loss) before provision (benefit) for credit losses	(147)	(182)	(295)	(369)
Provision (benefit) for credit losses	167	(292)	109	(592)
Income before income tax expense	(314)	110	(404)	223
Income tax expense (benefit)	(72)	13	(102)	28
NET INCOME	(242)	97	(302)	195
Total average assets	$ 53,448	$ 51,329	$ 51,558	$ 50,443