BUSINESS SEGMENTS - Schedule of Business Operating Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Net interest income	$ 1,562	$ 1,391
Noninterest income	606	544
Total revenue	2,168	1,935
Direct expenses	1,378	1,314
Indirect expenses	0	0
Total noninterest expense	1,378	1,314
Profit (loss) before provision for credit losses	790	621
Credit provision	140	153
Income before income tax expense	650	468
Income tax expense	133	95
NET INCOME	517	373
Total average assets	224,224	216,309
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,309	1,193
Noninterest income	299	297
Total revenue	1,608	1,490
Direct expenses	724	669
Indirect expenses	304	285
Total noninterest expense	1,028	954
Profit (loss) before provision for credit losses	580	536
Credit provision	71	86
Income before income tax expense	509	450
Income tax expense	131	114
NET INCOME	378	336
Total average assets	83,870	77,534
Depreciation and amortization	31	31
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	456	441
Noninterest income	263	215
Total revenue	719	656
Direct expenses	228	218
Indirect expenses	106	109
Total noninterest expense	334	327
Profit (loss) before provision for credit losses	385	329
Credit provision	64	77
Income before income tax expense	321	252
Income tax expense	78	56
NET INCOME	243	196
Total average assets	67,737	65,366
Depreciation and amortization	4	5
Other
Segment Reporting Information [Line Items]
Net interest income	(203)	(243)
Noninterest income	44	32
Total revenue	(159)	(211)
Direct expenses	426	427
Indirect expenses	(410)	(394)
Total noninterest expense	16	33
Profit (loss) before provision for credit losses	(175)	(244)
Credit provision	5	(10)
Income before income tax expense	(180)	(234)
Income tax expense	(76)	(75)
NET INCOME	(104)	(159)
Total average assets	72,617	73,409
Depreciation and amortization	$ 74	$ 75