ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Accruing and Nonaccruing Past Due Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Provision (benefit) for credit losses	$ 474	$ (411)	$ 1,616
Loans and leases	156,662	128,163
Loans and leases, nonaccrual	944	702
Loans and leases, nonaccrual with no related ACL	456	386
Financing Receivables, Current
Financing Receivable, Past Due [Line Items]
Loans and leases	154,527	126,308
Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	598	412
Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	226	166
Financing Receivables, 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	367	575
Commercial
Financing Receivable, Past Due [Line Items]
Loans and leases	82,180	60,350
Loans and leases, nonaccrual	352	183
Loans and leases, nonaccrual with no related ACL	71	37
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases	51,836	44,500
Loans and leases, nonaccrual	249	171
Loans and leases, nonaccrual with no related ACL	64	36
Commercial | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases	28,865	14,264
Loans and leases, nonaccrual	103	11
Loans and leases, nonaccrual with no related ACL	7	1
Commercial | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases	1,479	1,586
Loans and leases, nonaccrual	0	1
Loans and leases, nonaccrual with no related ACL	0	0
Commercial | Financing Receivables, Current
Financing Receivable, Past Due [Line Items]
Loans and leases	81,529	60,064
Commercial | Financing Receivables, Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases	51,389	44,247
Commercial | Financing Receivables, Current | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases	28,665	14,247
Commercial | Financing Receivables, Current | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases	1,475	1,570
Commercial | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	207	67
Commercial | Financing Receivables, 30 to 59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases	152	47
Commercial | Financing Receivables, 30 to 59 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases	51	6
Commercial | Financing Receivables, 30 to 59 Days Past Due | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases	4	14
Commercial | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	70	27
Commercial | Financing Receivables, 60 to 89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases	25	26
Commercial | Financing Receivables, 60 to 89 Days Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases	45	0
Commercial | Financing Receivables, 60 to 89 Days Past Due | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases	0	1
Commercial | Financing Receivables, 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	22	9
Commercial | Financing Receivables, 90 Days or More Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases	21	9
Commercial | Financing Receivables, 90 Days or More Past Due | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases	1	0
Commercial | Financing Receivables, 90 Days or More Past Due | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Retail
Financing Receivable, Past Due [Line Items]
Loans and leases	74,482	67,813
Loans and leases, nonaccrual	592	519
Loans and leases, nonaccrual with no related ACL	385	349
Retail | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases	29,921	22,822
Loans and leases, nonaccrual	234	201
Loans and leases, nonaccrual with no related ACL	187	137
Retail | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases	14,043	12,015
Loans and leases, nonaccrual	241	220
Loans and leases, nonaccrual with no related ACL	185	186
Retail | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases	12,292	14,549
Loans and leases, nonaccrual	56	55
Loans and leases, nonaccrual with no related ACL	9	22
Retail | Education
Financing Receivable, Past Due [Line Items]
Loans and leases	12,808	12,997
Loans and leases, nonaccrual	33	23
Loans and leases, nonaccrual with no related ACL	3	2
Retail | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases	5,418	5,430
Loans and leases, nonaccrual	28	20
Loans and leases, nonaccrual with no related ACL	1	2
Retail | FHA, VA And USDA Loans
Financing Receivable, Past Due [Line Items]
Loans and leases, 90 days or more past due and still accruing	316	544
Retail | Financing Receivables, Current
Financing Receivable, Past Due [Line Items]
Loans and leases	72,998	66,244
Retail | Financing Receivables, Current | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases	29,228	21,918
Retail | Financing Receivables, Current | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases	13,719	11,745
Retail | Financing Receivables, Current | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases	12,039	14,324
Retail | Financing Receivables, Current | Education
Financing Receivable, Past Due [Line Items]
Loans and leases	12,718	12,926
Retail | Financing Receivables, Current | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases	5,294	5,331
Retail | Financing Receivables, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	391	345
Retail | Financing Receivables, 30 to 59 Days Past Due | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases	95	102
Retail | Financing Receivables, 30 to 59 Days Past Due | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases	64	38
Retail | Financing Receivables, 30 to 59 Days Past Due | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases	152	131
Retail | Financing Receivables, 30 to 59 Days Past Due | Education
Financing Receivable, Past Due [Line Items]
Loans and leases	36	34
Retail | Financing Receivables, 30 to 59 Days Past Due | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases	44	40
Retail | Financing Receivables, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	156	139
Retail | Financing Receivables, 60 to 89 Days Past Due | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases	45	52
Retail | Financing Receivables, 60 to 89 Days Past Due | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases	19	12
Retail | Financing Receivables, 60 to 89 Days Past Due | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases	45	39
Retail | Financing Receivables, 60 to 89 Days Past Due | Education
Financing Receivable, Past Due [Line Items]
Loans and leases	17	13
Retail | Financing Receivables, 60 to 89 Days Past Due | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases	30	23
Retail | Financing Receivables, 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans and leases	345	566
Retail | Financing Receivables, 90 Days or More Past Due | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases	319	549
Retail | Financing Receivables, 90 Days or More Past Due | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Retail | Financing Receivables, 90 Days or More Past Due | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases	0	0
Retail | Financing Receivables, 90 Days or More Past Due | Education
Financing Receivable, Past Due [Line Items]
Loans and leases	4	1
Retail | Financing Receivables, 90 Days or More Past Due | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases	$ 22	$ 16