NONINTEREST INCOME - Components of Revenue from Contracts with Customers (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]
Revenue from contracts with customers	$ 452	$ 367	$ 1,202	$ 1,136
Total revenue from other sources	178	165	572	466
Total noninterest income	630	532	1,774	1,602
Bank-owned life insurance income	30	26	85	80
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	6	0	14
Total revenue from other sources	29	34	97	92
Total noninterest income	29	40	97	106
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	245	225	707	647
Total revenue from other sources	66	60	230	173
Total noninterest income	311	285	937	820
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	207	136	495	475
Total revenue from other sources	79	71	238	201
Total noninterest income	286	207	733	676
Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenue from other sources	4	0	7	0
Total noninterest income	4	0	7	0
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	111	109	330	310
Service charges and fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Service charges and fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	78	75	229	213
Service charges and fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	34	101	97
Service charges and fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85	91	252	266
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	6	0	13
Card fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	73	73	214	213
Card fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	12	38	40
Card fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158	88	348	330
Capital markets fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158	88	348	330
Capital markets fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Wealth fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	93	76	262	219
Wealth fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Wealth fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	93	76	262	219
Wealth fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Wealth fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	3	10	11
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	1
Other banking fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1	2	2
Other banking fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	2	8	8
Other banking fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0