LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Loans receivable
Loans, net of unearned income	$ 618,824	$ 617,617
Loans at fair value	$ 4,793	5,005
Corporate
Loans receivable
Number of days past due, non-accrual status	90 days
Number of days past due for reversal of accrued interest and charging to earnings	90 days
90 days past due and accruing	$ 194	280
Total non-accrual	2,327	1,596
Loans, total current	293,637	284,980
Loans, net of unearned income	300,924	291,832
Loans at fair value	4,760	4,971
Purchased distressed loans	$ 6	5
Loans less than this number of days past due are considered current	30 days
Corporate | Commercial and industrial
Loans receivable
90 days past due and accruing	$ 57	91
Total non-accrual	1,863	1,071
Loans, total current	124,241	118,530
Loans, net of unearned income	126,161	119,692
Corporate | Financial institutions
Loans receivable
90 days past due and accruing	0	16
Total non-accrual	164	173
Loans, total current	64,273	64,128
Loans, net of unearned income	64,437	64,317
Corporate | Mortgage and real estate
Loans receivable
90 days past due and accruing	119	144
Total non-accrual	204	232
Loans, total current	43,943	42,095
Loans, net of unearned income	44,266	42,471
Corporate | Leases
Loans receivable
90 days past due and accruing	0	0
Total non-accrual	1	76
Loans, total current	1,877	1,941
Loans, net of unearned income	1,878	2,017
Corporate | Other
Loans receivable
90 days past due and accruing	18	29
Total non-accrual	95	44
Loans, total current	59,303	58,286
Loans, net of unearned income	59,416	58,359
30 to 89 Days Past Due | Corporate
Loans receivable
90 days past due and accruing	193	269
30 to 89 Days Past Due | Corporate | Commercial and industrial
Loans receivable
90 days past due and accruing	57	87
30 to 89 Days Past Due | Corporate | Financial institutions
Loans receivable
90 days past due and accruing	0	16
30 to 89 Days Past Due | Corporate | Mortgage and real estate
Loans receivable
90 days past due and accruing	119	137
30 to 89 Days Past Due | Corporate | Leases
Loans receivable
90 days past due and accruing	0	0
30 to 89 Days Past Due | Corporate | Other
Loans receivable
90 days past due and accruing	17	29
Equal to greater than 90 days past due | Corporate
Loans receivable
90 days past due and accruing	1	11
Equal to greater than 90 days past due | Corporate | Commercial and industrial
Loans receivable
90 days past due and accruing	0	4
Equal to greater than 90 days past due | Corporate | Financial institutions
Loans receivable
90 days past due and accruing	0	0
Equal to greater than 90 days past due | Corporate | Mortgage and real estate
Loans receivable
90 days past due and accruing	0	7
Equal to greater than 90 days past due | Corporate | Leases
Loans receivable
90 days past due and accruing	0	0
Equal to greater than 90 days past due | Corporate | Other
Loans receivable
90 days past due and accruing	$ 1	$ 0