LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Non-Accrual Details
Loans, net of unearned income	$ 671,180	$ 667,034
Loans at fair value	3,000	4,374
Corporate
Non-Accrual Details
Past due and accruing	1,118	735
Total non-accrual	1,623	1,942
Total current	341,829	326,352
Loans, net of unearned income	347,548	333,378
Loans at fair value	$ 2,978	4,349
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	$ 657	262
Total non-accrual	1,095	1,506
Total current	147,195	139,554
Loans, net of unearned income	148,947	141,322
Corporate | Financial institutions
Non-Accrual Details
Past due and accruing	231	108
Total non-accrual	134	92
Total current	80,182	73,557
Loans, net of unearned income	80,547	73,757
Corporate | Mortgage and real estate
Non-Accrual Details
Past due and accruing	149	206
Total non-accrual	267	195
Total current	53,135	51,563
Loans, net of unearned income	53,551	51,964
Corporate | Leases
Non-Accrual Details
Past due and accruing	3	76
Total non-accrual	41	46
Total current	1,541	1,533
Loans, net of unearned income	1,585	1,655
Corporate | Other
Non-Accrual Details
Past due and accruing	78	83
Total non-accrual	86	103
Total current	59,776	60,145
Loans, net of unearned income	59,940	60,331
Corporate | 30 to 89 Days Past Due
Non-Accrual Details
Past due and accruing	997	627
Corporate | 30 to 89 Days Past Due | Commercial and industrial
Non-Accrual Details
Past due and accruing	618	249
Corporate | 30 to 89 Days Past Due | Financial institutions
Non-Accrual Details
Past due and accruing	177	93
Corporate | 30 to 89 Days Past Due | Mortgage and real estate
Non-Accrual Details
Past due and accruing	140	147
Corporate | 30 to 89 Days Past Due | Leases
Non-Accrual Details
Past due and accruing	3	68
Corporate | 30 to 89 Days Past Due | Other
Non-Accrual Details
Past due and accruing	59	70
Corporate | Equal to greater than 90 days past due and accruing
Non-Accrual Details
Past due and accruing	121	108
Corporate | Equal to greater than 90 days past due and accruing | Commercial and industrial
Non-Accrual Details
Past due and accruing	39	13
Corporate | Equal to greater than 90 days past due and accruing | Financial institutions
Non-Accrual Details
Past due and accruing	54	15
Corporate | Equal to greater than 90 days past due and accruing | Mortgage and real estate
Non-Accrual Details
Past due and accruing	9	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	$ 19	$ 13