LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financing receivable impaired
Carrying Value	$ 48	$ 4	$ 126	$ 56
TDRs involving changes in the amount and/or timing of principal payments	13	1	48	35
TDRs involving changes in the amount and/or timing of interest payments	0	0	0	18
TDRs involving changes in the amount and/or timing of both principal and interest payments	35	3	$ 78	3
Period within which default occurred post-modification			1 year
Number of days past due, default status			60 days
Carrying Value	587	612	$ 587	612
TDR in payment default	0	0	$ 1	0
Commercial market loans
Financing receivable impaired
Number of days past due, default status			90 days
Commercial and industrial
Financing receivable impaired
Carrying Value	13	1	$ 79	48
TDRs involving changes in the amount and/or timing of principal payments	12	0	45	30
TDRs involving changes in the amount and/or timing of interest payments	0	0	0	17
TDRs involving changes in the amount and/or timing of both principal and interest payments	1	1	34	1
Carrying Value	126	161	126	161
TDR in payment default	0	0	0	0
Financial institutions
Financing receivable impaired
Carrying Value	0	0	0	0
TDRs involving changes in the amount and/or timing of principal payments	0	0	0	0
TDRs involving changes in the amount and/or timing of interest payments	0	0	0	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	0	0	0	0
Carrying Value	1	0	1	0
TDR in payment default	0	0	1	0
Mortgage and real estate
Financing receivable impaired
Carrying Value	35	3	47	8
TDRs involving changes in the amount and/or timing of principal payments	1	1	3	5
TDRs involving changes in the amount and/or timing of interest payments	0	0	0	1
TDRs involving changes in the amount and/or timing of both principal and interest payments	34	2	44	2
Carrying Value	144	125	144	125
TDR in payment default	0	0	0	0
Other
Financing receivable impaired
Carrying Value	0	0	0	0
TDRs involving changes in the amount and/or timing of principal payments	0	0	0	0
TDRs involving changes in the amount and/or timing of interest payments	0	0	0	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	0	0	0	0
Carrying Value	316	326	316	326
TDR in payment default	$ 0	$ 0	$ 0	$ 0