LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Non-Accrual Details
Loans, net of unearned income	$ 672,938	$ 667,034
Loans at fair value	4,536	4,374
Corporate
Non-Accrual Details
Past due and accruing	1,002	735
Total non-accrual	1,668	1,942
Total current	340,671	326,352
Loans, net of unearned income	347,854	333,378
Loans at fair value	4,513	4,349
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
Past due and accruing	$ 555	262
Total non-accrual	1,260	1,506
Total current	149,912	139,554
Loans, net of unearned income	151,727	141,322
Corporate | Financial institutions
Non-Accrual Details
Past due and accruing	85	108
Total non-accrual	87	92
Total current	74,840	73,557
Loans, net of unearned income	75,012	73,757
Corporate | Mortgage and real estate
Non-Accrual Details
Past due and accruing	145	206
Total non-accrual	192	195
Total current	52,772	51,563
Loans, net of unearned income	53,109	51,964
Corporate | Leases
Non-Accrual Details
Past due and accruing	22	76
Total non-accrual	43	46
Total current	1,564	1,533
Loans, net of unearned income	1,629	1,655
Corporate | Other
Non-Accrual Details
Past due and accruing	195	83
Total non-accrual	86	103
Total current	61,583	60,145
Loans, net of unearned income	61,864	60,331
Corporate | 30 to 89 Days Past Due
Non-Accrual Details
Past due and accruing	882	627
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Non-Accrual Details
Past due and accruing	478	249
Corporate | 30 to 89 Days Past Due | Financial institutions
Non-Accrual Details
Past due and accruing	63	93
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Non-Accrual Details
Past due and accruing	131	147
Corporate | 30 to 89 Days Past Due | Leases
Non-Accrual Details
Past due and accruing	22	68
Corporate | 30 to 89 Days Past Due | Other
Non-Accrual Details
Past due and accruing	188	70
Corporate | Equal to greater than 90 days past due and accruing
Non-Accrual Details
Past due and accruing	120	108
Corporate | Equal to greater than 90 days past due and accruing | Commercial and industrial
Non-Accrual Details
Past due and accruing	77	13
Corporate | Equal to greater than 90 days past due and accruing | Financial institutions
Non-Accrual Details
Past due and accruing	22	15
Corporate | Equal to greater than 90 days past due and accruing | Mortgage and real estate
Non-Accrual Details
Past due and accruing	14	59
Corporate | Equal to greater than 90 days past due and accruing | Leases
Non-Accrual Details
Past due and accruing	0	8
Corporate | Equal to greater than 90 days past due and accruing | Other
Non-Accrual Details
Past due and accruing	$ 7	$ 13