NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 383	$ 402	$ 750	$ 769
Total revenue from other sources	217	151	394	301
Total noninterest income	600	553	1,144	1,070
Bank-owned life insurance income	28	30	55	54
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	5	0	8
Total revenue from other sources	36	29	68	58
Total noninterest income	36	34	68	66
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	239	224	462	422
Total revenue from other sources	90	53	164	113
Total noninterest income	329	277	626	535
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	144	173	288	339
Total revenue from other sources	88	69	159	130
Total noninterest income	232	242	447	469
Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenue from other sources	3	0	3	0
Total noninterest income	3	0	3	0
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	111	105	219	201
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	77	75	151	138
Service charges and fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	30	68	63
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	87	91	167	175
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	4	0	7
Card fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74	74	141	140
Card fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	13	26	28
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	95	126	190	242
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	95	126	190	242
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	88	75	169	143
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	88	75	169	143
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	2	5	5	8
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	0	1
Other banking fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	1	1
Other banking fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	4	4	6
Other banking fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0