REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	$ 424	$ 362	$ 1,152	$ 1,058
Noninterest income within the scope of other GAAP topics	204	161	441	423
Noninterest income	628	523	1,593	1,481
Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	161	143	451	419
Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	104	93	307	271
Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	66	58	182	168
Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	46	37	117	109
Noninterest income	94	78	245	207
Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	2	10	9	30
Noninterest income	23	19	47	60
Insurance income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	20	17	59	54
Noninterest income	20	18	59	55
Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	25	4	27	7
Operating Segments | Consumer & Regional Banking
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	330	283	903	828
Noninterest income within the scope of other GAAP topics	63	55	156	140
Noninterest income	393	338	1,059	968
Operating Segments | Consumer & Regional Banking | Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	120	114	345	335
Operating Segments | Consumer & Regional Banking | Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	96	89	289	262
Operating Segments | Consumer & Regional Banking | Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	62	57	172	160
Operating Segments | Consumer & Regional Banking | Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	10	5	16	16
Operating Segments | Consumer & Regional Banking | Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	1	1	2	2
Operating Segments | Consumer & Regional Banking | Insurance income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	16	15	52	47
Operating Segments | Consumer & Regional Banking | Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	25	2	27	6
Operating Segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	96	81	253	233
Noninterest income within the scope of other GAAP topics	122	100	304	257
Noninterest income	218	181	557	490
Operating Segments | Commercial Banking | Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	41	29	106	84
Operating Segments | Commercial Banking | Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	8	4	18	9
Operating Segments | Commercial Banking | Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	4	1	10	8
Operating Segments | Commercial Banking | Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	37	32	102	93
Operating Segments | Commercial Banking | Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	1	9	7	28
Operating Segments | Commercial Banking | Insurance income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	4	3	7	8
Operating Segments | Commercial Banking | Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	1	3	3	3
Treasury / Other
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	(2)	(2)	(4)	(3)
Noninterest income within the scope of other GAAP topics	19	6	(19)	26
Noninterest income	17	4	(23)	23
Treasury / Other | Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0	0	0
Treasury / Other | Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0	0	0
Treasury / Other | Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0	0	0
Treasury / Other | Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	(1)	0	(1)	0
Treasury / Other | Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0	0	0
Treasury / Other | Insurance income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	(1)	0	(1)
Treasury / Other | Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	$ (1)	$ (1)	$ (3)	$ (2)