LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Non-Accrual Details
Loans, net of unearned income	$ 682,346	$ 684,196
Loans at fair value	3,874	3,223
Corporate
Non-Accrual Details
Past due and accruing	1,447	852
Total non-accrual	1,482	1,311
Total current	355,676	348,343
Loans, net of unearned income	362,459	353,709
Loans at fair value	$ 3,854	3,203
Number of days past due, non-accrual status	90 days
Loans less than this number of days past due are considered current	30 days
Corporate | Commercial and industrial
Non-Accrual Details
Past due and accruing	$ 580	407
Total non-accrual	1,177	919
Total current	151,074	143,960
Loans, net of unearned income	152,831	145,286
Corporate | Financial institutions
Non-Accrual Details
Past due and accruing	437	94
Total non-accrual	92	102
Total current	86,487	83,672
Loans, net of unearned income	87,016	83,868
Corporate | Mortgage and real estate
Non-Accrual Details
Past due and accruing	191	133
Total non-accrual	182	215
Total current	56,359	57,116
Loans, net of unearned income	56,732	57,464
Corporate | Leases
Non-Accrual Details
Past due and accruing	35	15
Total non-accrual	0	0
Total current	1,465	1,516
Loans, net of unearned income	1,500	1,531
Corporate | Other
Non-Accrual Details
Past due and accruing	204	203
Total non-accrual	31	75
Total current	60,291	62,079
Loans, net of unearned income	60,526	62,357
Corporate | 30 to 89 Days Past Due
Non-Accrual Details
Past due and accruing	1,091	736
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Non-Accrual Details
Past due and accruing	455	365
Corporate | 30 to 89 Days Past Due | Financial institutions
Non-Accrual Details
Past due and accruing	301	87
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Non-Accrual Details
Past due and accruing	191	128
Corporate | 30 to 89 Days Past Due | Leases
Non-Accrual Details
Past due and accruing	16	5
Corporate | 30 to 89 Days Past Due | Other
Non-Accrual Details
Past due and accruing	128	151
Corporate | Equal to greater than 90 days past due and accruing
Non-Accrual Details
Past due and accruing	356	116
Corporate | Equal to greater than 90 days past due and accruing | Commercial and industrial
Non-Accrual Details
Past due and accruing	125	42
Corporate | Equal to greater than 90 days past due and accruing | Financial institutions
Non-Accrual Details
Past due and accruing	136	7
Corporate | Equal to greater than 90 days past due and accruing | Mortgage and real estate
Non-Accrual Details
Past due and accruing	0	5
Corporate | Equal to greater than 90 days past due and accruing | Leases
Non-Accrual Details
Past due and accruing	19	10
Corporate | Equal to greater than 90 days past due and accruing | Other
Non-Accrual Details
Past due and accruing	$ 76	$ 52