NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,266	$ 1,299	$ 1,325
Total noninterest income	1,983	2,009	2,135
Bank-owned life insurance	93	88	67
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	717	710	810
Total noninterest income	1,983	2,009	2,135
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	4	0
Total revenue from other sources	131	97	103
Total noninterest income	132	101	103
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	783	769	757
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	284	294	466
Total noninterest income	1,067	1,063	1,223
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	482	526	568
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	302	319	241
Total noninterest income	784	845	809
Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Non-Core | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	0	0	0
Total noninterest income	0	0	0
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	409	418	407
Service charges and fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	3	0
Service charges and fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	277	291	302
Service charges and fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	131	124	105
Service charges and fees | Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	291	271	248
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Card fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	244	228	216
Card fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47	43	32
Card fees | Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	293	341	419
Capital markets fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Capital markets fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Capital markets fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	293	341	419
Capital markets fees | Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	259	250	239
Trust and investment services fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Trust and investment services fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	259	249	239
Trust and investment services fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	0
Trust and investment services fees | Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	19	12
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	0
Other banking fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	1	0
Other banking fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	17	12
Other banking fees | Non-Core
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0