BUSINESS SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Net interest income	$ 1,488	$ 1,369	$ 4,316	$ 4,221
Noninterest income	630	532	1,774	1,602
Total revenue	2,118	1,901	6,090	5,823
Direct expenses	1,335	1,259	3,968	3,918
Indirect expenses	0	0	0	0
Total noninterest expense	1,335	1,259	3,968	3,918
Profit (loss) before provision for credit losses	783	642	2,122	1,905
Credit provision	154	172	471	525
Income before income tax expense	629	470	1,651	1,380
Income tax expense	135	88	348	272
NET INCOME	494	382	1,303	1,108
Total average assets	219,117	218,578	217,706	219,520
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,262	1,156	3,673	3,369
Noninterest income	311	285	937	820
Total revenue	1,573	1,441	4,610	4,189
Direct expenses	692	586	2,040	1,728
Indirect expenses	287	330	856	1,006
Total noninterest expense	979	916	2,896	2,734
Profit (loss) before provision for credit losses	594	525	1,714	1,455
Credit provision	81	84	248	249
Income before income tax expense	513	441	1,466	1,206
Income tax expense	130	114	371	311
NET INCOME	383	327	1,095	895
Total average assets	80,729	75,392	79,040	74,510
Depreciation and amortization	30	29	92	84
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	448	478	1,328	1,486
Noninterest income	286	207	733	676
Total revenue	734	685	2,061	2,162
Direct expenses	223	205	660	626
Indirect expenses	110	95	317	302
Total noninterest expense	333	300	977	928
Profit (loss) before provision for credit losses	401	385	1,084	1,234
Credit provision	78	91	239	262
Income before income tax expense	323	294	845	972
Income tax expense	75	63	195	223
NET INCOME	248	231	650	749
Total average assets	66,134	68,092	65,931	69,046
Depreciation and amortization	5	6	15	21
Operating Segments | Non-Core
Segment Reporting Information [Line Items]
Net interest income	(7)	(28)	(27)	(96)
Noninterest income	4	0	7	0
Total revenue	(3)	(28)	(20)	(96)
Direct expenses	1	1	2	3
Indirect expenses	11	22	41	71
Total noninterest expense	12	23	43	74
Profit (loss) before provision for credit losses	(15)	(51)	(63)	(170)
Credit provision	4	17	43	46
Income before income tax expense	(19)	(68)	(106)	(216)
Income tax expense	(5)	(17)	(27)	(55)
NET INCOME	(14)	(51)	(79)	(161)
Total average assets	4,000	8,389	5,241	9,450
Depreciation and amortization			230	233
Other
Segment Reporting Information [Line Items]
Net interest income	(215)	(237)	(658)	(538)
Noninterest income	29	40	97	106
Total revenue	(186)	(197)	(561)	(432)
Direct expenses	419	467	1,266	1,561
Indirect expenses	(408)	(447)	(1,214)	(1,379)
Total noninterest expense	11	20	52	182
Profit (loss) before provision for credit losses	(197)	(217)	(613)	(614)
Credit provision	(9)	(20)	(59)	(32)
Income before income tax expense	(188)	(197)	(554)	(582)
Income tax expense	(65)	(72)	(191)	(207)
NET INCOME	(123)	(125)	(363)	(375)
Total average assets	68,254	$ 66,705	$ 67,494	66,514
Depreciation and amortization	$ 77			$ 79