LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Loans receivable
Loans, net of unearned income	$ 688,670	$ 684,196
Loans at fair value	3,824	3,223
Corporate
Loans receivable
Past due and accruing	1,237	852
Total non-accrual	1,410	1,311
Total current	356,224	348,343
Loans, net of unearned income	362,675	353,709
Loans at fair value	$ 3,804	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
Loans receivable
Past due and accruing	$ 505	407
Total non-accrual	1,064	919
Total current	149,418	143,960
Loans, net of unearned income	150,987	145,286
Corporate | Financial institutions
Loans receivable
Past due and accruing	260	94
Total non-accrual	36	102
Total current	82,983	83,672
Loans, net of unearned income	83,279	83,868
Corporate | Mortgage and real estate
Loans receivable
Past due and accruing	238	133
Total non-accrual	204	215
Total current	58,438	57,116
Loans, net of unearned income	58,880	57,464
Corporate | Lease financing
Loans receivable
Past due and accruing	19	15
Total non-accrual	0	0
Total current	1,458	1,516
Loans, net of unearned income	1,477	1,531
Corporate | Other
Loans receivable
Past due and accruing	215	203
Total non-accrual	106	75
Total current	63,927	62,079
Loans, net of unearned income	64,248	62,357
Corporate | 30 to 89 Days Past Due
Loans receivable
Past due and accruing	1,111	736
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Loans receivable
Past due and accruing	473	365
Corporate | 30 to 89 Days Past Due | Financial institutions
Loans receivable
Past due and accruing	245	87
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Loans receivable
Past due and accruing	234	128
Corporate | 30 to 89 Days Past Due | Lease financing
Loans receivable
Past due and accruing	0	5
Corporate | 30 to 89 Days Past Due | Other
Loans receivable
Past due and accruing	159	151
Corporate | Equal to greater than 90 days past due and accruing
Loans receivable
Past due and accruing	126	116
Corporate | Equal to greater than 90 days past due and accruing | Commercial and industrial
Loans receivable
Past due and accruing	32	42
Corporate | Equal to greater than 90 days past due and accruing | Financial institutions
Loans receivable
Past due and accruing	15	7
Corporate | Equal to greater than 90 days past due and accruing | Mortgage and real estate
Loans receivable
Past due and accruing	4	5
Corporate | Equal to greater than 90 days past due and accruing | Lease financing
Loans receivable
Past due and accruing	19	10
Corporate | Equal to greater than 90 days past due and accruing | Other
Loans receivable
Past due and accruing	$ 56	$ 52