NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 402	$ 323	$ 769	$ 632
Total revenue from other sources	151	183	301	359
Total noninterest income	553	506	1,070	991
Bank-owned life insurance income	30	23	54	46
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	0	8	0
Total revenue from other sources	29	31	58	59
Total noninterest income	34	31	66	59
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	224	198	422	388
Total revenue from other sources	53	70	113	136
Total noninterest income	277	268	535	524
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	173	125	339	244
Total revenue from other sources	69	82	130	164
Total noninterest income	242	207	469	408
Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenue from other sources	0	0	0	0
Total noninterest income	0	0	0	0
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	105	101	201	200
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	75	66	138	133
Service charges and fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30	35	63	67
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	91	78	175	149
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	0	7	0
Card fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74	67	140	126
Card fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	11	28	23
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	126	76	242	147
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	126	76	242	147
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	75	65	143	128
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	75	65	143	128
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	8	8
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0	1	0
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	4	3	6	7
Other banking fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0