LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Non-Accrual Details
Loans, net of unearned income	$ 628,595	$ 624,369
Loans at fair value	4,035	3,486
Corporate
Non-Accrual Details
90 days past due and accruing	1,150	997
Total non-accrual	2,339	2,421
Total current	300,543	292,431
Loans, net of unearned income	308,039	299,306
Loans at fair value	4,007	3,457
Purchased distressed loans	$ 0	0
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	$ 170	195
Total non-accrual	1,692	1,909
Total current	132,583	127,012
Loans, net of unearned income	134,445	129,116
Corporate | Financial institutions
Non-Accrual Details
90 days past due and accruing	233	121
Total non-accrual	301	185
Total current	67,478	61,254
Loans, net of unearned income	68,012	61,560
Corporate | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	211	285
Total non-accrual	181	139
Total current	45,172	43,607
Loans, net of unearned income	45,564	44,031
Corporate | Leases
Non-Accrual Details
90 days past due and accruing	106	35
Total non-accrual	67	56
Total current	1,591	1,678
Loans, net of unearned income	1,764	1,769
Corporate | Other
Non-Accrual Details
90 days past due and accruing	430	361
Total non-accrual	98	132
Total current	53,719	58,880
Loans, net of unearned income	54,247	59,373
Corporate | 30 to 89 Days Past Due
Non-Accrual Details
90 days past due and accruing	1,121	786
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Non-Accrual Details
90 days past due and accruing	170	143
Corporate | 30 to 89 Days Past Due | Financial institutions
Non-Accrual Details
90 days past due and accruing	215	119
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	211	148
Corporate | 30 to 89 Days Past Due | Leases
Non-Accrual Details
90 days past due and accruing	98	27
Corporate | 30 to 89 Days Past Due | Other
Non-Accrual Details
90 days past due and accruing	427	349
Corporate | Equal to greater than 90 days past due
Non-Accrual Details
90 days past due and accruing	29	211
Corporate | Equal to greater than 90 days past due | Commercial and industrial
Non-Accrual Details
90 days past due and accruing	0	52
Corporate | Equal to greater than 90 days past due | Financial institutions
Non-Accrual Details
90 days past due and accruing	18	2
Corporate | Equal to greater than 90 days past due | Mortgage and real estate
Non-Accrual Details
90 days past due and accruing	0	137
Corporate | Equal to greater than 90 days past due | Leases
Non-Accrual Details
90 days past due and accruing	8	8
Corporate | Equal to greater than 90 days past due | Other
Non-Accrual Details
90 days past due and accruing	$ 3	$ 12