NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 309	$ 300
Total noninterest income	485	498
Bank-owned life insurance income	23	21
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	176	198
Total noninterest income	485	498
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	2
Total revenue from other sources	28	26
Total noninterest income	28	28
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	190	181
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	66	76
Total noninterest income	256	257
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	119	117
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	82	96
Total noninterest income	201	213
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	99	97
Service charges and fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1
Service charges and fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	67	69
Service charges and fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32	27
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	71	60
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Card fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	59	50
Card fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	10
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	71	78
Capital markets fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Capital markets fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Capital markets fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	71	78
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	63	61
Trust and investment services fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Trust and investment services fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	63	61
Trust and investment services fees | Commercial Banking
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	5	4
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1
Other banking fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1
Other banking fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 4	$ 2