NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 322	$ 307	$ 961	$ 902
Total noninterest income	512	514	1,504	1,541
Bank-owned life insurance income	22	17	64	47
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	190	207	543	639
Total noninterest income	512	514	1,504	1,541
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0	4	0
Total revenue from other sources	28	31	46	76
Total noninterest income	29	31	50	76
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	194	200	574	569
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	76	115	233	380
Total noninterest income	270	315	807	949
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	127	107	383	333
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	86	61	264	183
Total noninterest income	213	168	647	516
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	109	109	314	308
Service charges and fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0	3	0
Service charges and fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74	82	217	230
Service charges and fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	27	94	78
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	70	65	200	183
Card fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Card fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	59	57	169	160
Card fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	8	31	23
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	69	244	225
Capital markets fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	69	244	225
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61	61	188	179
Trust and investment services fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Trust and investment services fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61	61	188	179
Trust and investment services fees | Commercial Banking
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	6	3	15	7
Other banking fees | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	1	0
Other banking fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other banking fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 7	$ 3	$ 14	$ 7