NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 415	$ 367
Total revenue from other sources	191	177
Total noninterest income	606	544
Bank-owned life insurance income	29	27
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	0
Total revenue from other sources	40	32
Total noninterest income	44	32
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	242	223
Total revenue from other sources	57	74
Total noninterest income	299	297
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	169	144
Total revenue from other sources	94	71
Total noninterest income	263	215
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	111	108
Service charges and fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Service charges and fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	74
Service charges and fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	35	34
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	120	95
Capital markets fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Capital markets fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Capital markets fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	120	95
Wealth fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	100	81
Wealth fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Wealth fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	100	81
Wealth fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	80	80
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	0
Card fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	65	67
Card fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	13
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	3
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other banking fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1
Other banking fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 3	$ 2