NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 367	$ 367
Total revenue from other sources	177	150
Total noninterest income	544	517
Bank-owned life insurance income	27	24
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	3
Total revenue from other sources	32	29
Total noninterest income	32	32
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	223	198
Total revenue from other sources	74	60
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	144	166
Total revenue from other sources	71	61
Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Total revenue from other sources	0	0
Total noninterest income	0	0
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	108	96
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	74	63
Service charges and fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	33
Service charges and fees | Non-Core | 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	84
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	3
Card fees | Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	67	66
Card fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	15
Card fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	95	116
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	95	116
Capital markets fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Wealth fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	68
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	81	68
Wealth fees | Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Wealth fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	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	2	2
Other banking fees | Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0