BUSINESS SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Net interest income	$ 1,391	$ 1,442
Noninterest income	544	517
Total revenue	1,935	1,959
Direct expenses	1,314	1,358
Indirect expenses	0	0
Total noninterest expense	1,314	1,358
Profit (loss) before provision for credit losses	621	601
Credit provision	153	171
Income before income tax expense	468	430
Income tax expense	95	96
NET INCOME	373	334
Total average assets	216,309	220,770
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,193	1,093
Noninterest income	297	258
Total revenue	1,490	1,351
Direct expenses	669	576
Indirect expenses	285	327
Total noninterest expense	954	903
Profit (loss) before provision for credit losses	536	448
Credit provision	86	81
Income before income tax expense	450	367
Income tax expense	114	95
NET INCOME	336	272
Total average assets	77,534	73,833
Depreciation and amortization	31	27
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	441	514
Noninterest income	215	227
Total revenue	656	741
Direct expenses	218	213
Indirect expenses	109	104
Total noninterest expense	327	317
Profit (loss) before provision for credit losses	329	424
Credit provision	77	81
Income before income tax expense	252	343
Income tax expense	56	84
NET INCOME	196	259
Total average assets	65,366	70,100
Depreciation and amortization	5	7
Operating Segments | Non-Core
Segment Reporting Information [Line Items]
Net interest income	(15)	(37)
Noninterest income	0	0
Total revenue	(15)	(37)
Direct expenses	0	1
Indirect expenses	16	24
Total noninterest expense	16	25
Profit (loss) before provision for credit losses	(31)	(62)
Credit provision	37	19
Income before income tax expense	(68)	(81)
Income tax expense	(17)	(21)
NET INCOME	(51)	(60)
Total average assets	6,536	10,554
Other
Segment Reporting Information [Line Items]
Net interest income	(228)	(128)
Noninterest income	32	32
Total revenue	(196)	(96)
Direct expenses	427	568
Indirect expenses	(410)	(455)
Total noninterest expense	17	113
Profit (loss) before provision for credit losses	(213)	(209)
Credit provision	(47)	(10)
Income before income tax expense	(166)	(199)
Income tax expense	(58)	(62)
NET INCOME	(108)	(137)
Total average assets	66,873	66,283
Depreciation and amortization	$ 75	$ 77