CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Accruing and Nonaccruing Past Due Amounts (Details) - USD ($) $ in Millions		Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Loans and leases	[1]	$ 151,320	$ 156,662
Loans and leases, nonaccrual		1,191	944
Loans and leases, nonaccrual with no related ACL		405	456
Current
Financing Receivable, Past Due [Line Items]
Loans and leases		149,246	154,527
30-59
Financing Receivable, Past Due [Line Items]
Loans and leases		391	598
60-89
Financing Receivable, Past Due [Line Items]
Loans and leases		210	226
90+
Financing Receivable, Past Due [Line Items]
Loans and leases		282	367
Commercial
Financing Receivable, Past Due [Line Items]
Loans and leases		78,279	82,180
Loans and leases, nonaccrual		635	352
Loans and leases, nonaccrual with no related ACL		95	71
Commercial | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases		48,038	51,836
Loans and leases, nonaccrual		280	249
Loans and leases, nonaccrual with no related ACL		72	64
Commercial | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases		28,947	28,865
Loans and leases, nonaccrual		352	103
Loans and leases, nonaccrual with no related ACL		23	7
Commercial | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases		1,294	1,479
Loans and leases, nonaccrual		3	0
Loans and leases, nonaccrual with no related ACL		0	0
Commercial | Current
Financing Receivable, Past Due [Line Items]
Loans and leases		77,532	81,529
Commercial | Current | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases		47,727	51,389
Commercial | Current | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases		28,514	28,665
Commercial | Current | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases		1,291	1,475
Commercial | 30-59
Financing Receivable, Past Due [Line Items]
Loans and leases		42	207
Commercial | 30-59 | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases		18	152
Commercial | 30-59 | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases		24	51
Commercial | 30-59 | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases		0	4
Commercial | 60-89
Financing Receivable, Past Due [Line Items]
Loans and leases		68	70
Commercial | 60-89 | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases		11	25
Commercial | 60-89 | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases		57	45
Commercial | 60-89 | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases		0	0
Commercial | 90+
Financing Receivable, Past Due [Line Items]
Loans and leases		2	22
Commercial | 90+ | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Loans and leases		2	21
Commercial | 90+ | Commercial real estate
Financing Receivable, Past Due [Line Items]
Loans and leases		0	1
Commercial | 90+ | Leases
Financing Receivable, Past Due [Line Items]
Loans and leases		0	0
Retail
Financing Receivable, Past Due [Line Items]
Loans and leases		73,041	74,482
Loans and leases, nonaccrual		556	592
Loans and leases, nonaccrual with no related ACL		310	385
Retail | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases		30,769	29,921
Loans and leases, nonaccrual		201	234
Loans and leases, nonaccrual with no related ACL		145	187
Retail | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases		14,487	14,043
Loans and leases, nonaccrual		251	241
Loans and leases, nonaccrual with no related ACL		155	185
Retail | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases		10,428	12,292
Loans and leases, nonaccrual		51	56
Loans and leases, nonaccrual with no related ACL		6	9
Retail | Education
Financing Receivable, Past Due [Line Items]
Loans and leases		12,246	12,808
Loans and leases, nonaccrual		22	33
Loans and leases, nonaccrual with no related ACL		3	3
Retail | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases		5,111	5,418
Loans and leases, nonaccrual		31	28
Loans and leases, nonaccrual with no related ACL		1	1
Retail | FHA, VA And USDA Loans
Financing Receivable, Past Due [Line Items]
Loans and leases, 90 days or more past due and still accruing		256	316
Retail | Current
Financing Receivable, Past Due [Line Items]
Loans and leases		71,714	72,998
Retail | Current | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases		30,189	29,228
Retail | Current | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases		14,157	13,719
Retail | Current | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases		10,207	12,039
Retail | Current | Education
Financing Receivable, Past Due [Line Items]
Loans and leases		12,169	12,718
Retail | Current | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases		4,992	5,294
Retail | 30-59
Financing Receivable, Past Due [Line Items]
Loans and leases		349	391
Retail | 30-59 | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases		90	95
Retail | 30-59 | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases		55	64
Retail | 30-59 | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases		130	152
Retail | 30-59 | Education
Financing Receivable, Past Due [Line Items]
Loans and leases		33	36
Retail | 30-59 | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases		41	44
Retail | 60-89
Financing Receivable, Past Due [Line Items]
Loans and leases		142	156
Retail | 60-89 | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases		32	45
Retail | 60-89 | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases		24	19
Retail | 60-89 | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases		40	45
Retail | 60-89 | Education
Financing Receivable, Past Due [Line Items]
Loans and leases		19	17
Retail | 60-89 | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases		27	30
Retail | 90+
Financing Receivable, Past Due [Line Items]
Loans and leases		280	345
Retail | 90+ | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans and leases		257	319
Retail | 90+ | Home equity
Financing Receivable, Past Due [Line Items]
Loans and leases		0	0
Retail | 90+ | Automobile
Financing Receivable, Past Due [Line Items]
Loans and leases		0	0
Retail | 90+ | Education
Financing Receivable, Past Due [Line Items]
Loans and leases		3	4
Retail | 90+ | Other retail
Financing Receivable, Past Due [Line Items]
Loans and leases		$ 20	$ 22

[1] Includes amounts in consolidated VIEs. See Note 6 for additional information.