BUSINESS SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Net interest income	$ 1,437	$ 1,410	$ 2,828	$ 2,852
Noninterest income	600	553	1,144	1,070
Total revenue	2,037	1,963	3,972	3,922
Direct expenses	1,319	1,301	2,633	2,659
Indirect expenses	0	0	0	0
Total noninterest expense	1,319	1,301	2,633	2,659
Profit (loss) before provision for credit losses	718	662	1,339	1,263
Credit provision	164	182	317	353
Income before income tax expense	554	480	1,022	910
Income tax expense	118	88	213	184
NET INCOME	436	392	809	726
Total average assets	217,661	219,222	216,989	219,996
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,218	1,120	2,411	2,213
Noninterest income	329	277	626	535
Total revenue	1,547	1,397	3,037	2,748
Direct expenses	679	566	1,348	1,142
Indirect expenses	284	349	569	676
Total noninterest expense	963	915	1,917	1,818
Profit (loss) before provision for credit losses	584	482	1,120	930
Credit provision	81	84	167	165
Income before income tax expense	503	398	953	765
Income tax expense	127	102	241	197
NET INCOME	376	296	712	568
Total average assets	78,822	74,295	78,182	74,064
Depreciation and amortization	32	28	61	55
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	439	494	880	1,008
Noninterest income	232	242	447	469
Total revenue	671	736	1,327	1,477
Direct expenses	219	208	437	421
Indirect expenses	98	103	207	207
Total noninterest expense	317	311	644	628
Profit (loss) before provision for credit losses	354	425	683	849
Credit provision	84	90	161	171
Income before income tax expense	270	335	522	678
Income tax expense	64	76	120	160
NET INCOME	206	259	402	518
Total average assets	66,284	68,958	65,827	69,529
Depreciation and amortization	5	7	10	14
Operating Segments | Non-Core
Segment Reporting Information [Line Items]
Net interest income	(5)	(31)	(20)	(68)
Noninterest income	3	0	3	0
Total revenue	(2)	(31)	(17)	(68)
Direct expenses	1	1	1	2
Indirect expenses	14	25	30	49
Total noninterest expense	15	26	31	51
Profit (loss) before provision for credit losses	(17)	(57)	(48)	(119)
Credit provision	2	10	39	29
Income before income tax expense	(19)	(67)	(87)	(148)
Income tax expense	(5)	(17)	(22)	(38)
NET INCOME	(14)	(50)	(65)	(110)
Total average assets	5,216	9,418	5,872	9,986
Depreciation and amortization			155	155
Other
Segment Reporting Information [Line Items]
Net interest income	(215)	(173)	(443)	(301)
Noninterest income	36	34	68	66
Total revenue	(179)	(139)	(375)	(235)
Direct expenses	420	526	847	1,094
Indirect expenses	(396)	(477)	(806)	(932)
Total noninterest expense	24	49	41	162
Profit (loss) before provision for credit losses	(203)	(188)	(416)	(397)
Credit provision	(3)	(2)	(50)	(12)
Income before income tax expense	(200)	(186)	(366)	(385)
Income tax expense	(68)	(73)	(126)	(135)
NET INCOME	(132)	(113)	(240)	(250)
Total average assets	67,339	$ 66,551	$ 67,108	66,417
Depreciation and amortization	$ 77			$ 78