LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Non-Accrual Details
Loans, net of unearned income	$ 638,435	$ 617,617
Loans at fair value	3,970	5,005
Corporate
Non-Accrual Details
90 days past due and accruing	1,012	280
Total non-accrual	2,415	1,596
Loans, total current	302,367	284,980
Loans, net of unearned income	309,733	291,832
Loans at fair value	3,939	4,971
Purchased distressed loans	$ 0	5
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
90 days past due and accruing	$ 212	91
Total non-accrual	1,940	1,071
Loans, total current	129,531	118,465
Loans, net of unearned income	131,683	119,627
Corporate | Financial institutions
Non-Accrual Details
90 days past due and accruing	0	16
Total non-accrual	189	173
Loans, total current	62,283	64,128
Loans, net of unearned income	62,472	64,317
Corporate | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	351	144
Total non-accrual	169	232
Loans, total current	46,051	42,095
Loans, net of unearned income	46,571	42,471
Corporate | Leases
Non-Accrual Details
90 days past due and accruing	179	0
Total non-accrual	58	76
Loans, total current	1,537	2,006
Loans, net of unearned income	1,774	2,082
Corporate | Other
Non-Accrual Details
90 days past due and accruing	270	29
Total non-accrual	59	44
Loans, total current	62,965	58,286
Loans, net of unearned income	63,294	58,359
Corporate | 30 to 89 Days Past Due
Non-Accrual Details
90 days past due and accruing	959	269
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Non-Accrual Details
90 days past due and accruing	208	87
Corporate | 30 to 89 Days Past Due | Financial institutions
Non-Accrual Details
90 days past due and accruing	0	16
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	351	137
Corporate | 30 to 89 Days Past Due | Leases
Non-Accrual Details
90 days past due and accruing	131	0
Corporate | 30 to 89 Days Past Due | Other
Non-Accrual Details
90 days past due and accruing	269	29
Corporate | Equal to greater than 90 days past due
Non-Accrual Details
90 days past due and accruing	53	11
Corporate | Equal to greater than 90 days past due | Commercial and industrial
Non-Accrual Details
90 days past due and accruing	4	4
Corporate | Equal to greater than 90 days past due | Financial institutions
Non-Accrual Details
90 days past due and accruing	0	0
Corporate | Equal to greater than 90 days past due | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	0	7
Corporate | Equal to greater than 90 days past due | Leases
Non-Accrual Details
90 days past due and accruing	48	0
Corporate | Equal to greater than 90 days past due | Other
Non-Accrual Details
90 days past due and accruing	$ 1	$ 0