LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing receivable impaired
Carrying Value	$ 248	$ 77	$ 350	$ 78
TDRs involving changes in the amount and/or timing of principal payments	73	34	73	35
TDRs involving changes in the amount and/or timing of interest payments	174	0	174	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	1	43	$ 103	43
Period within which default occurred post-modification			1 year
Number of days past due, default status			60 days
Carrying Value	741	558	$ 741	558
TDR in payment default	7	1	$ 7	1
Commercial banking loans
Financing receivable impaired
Number of days past due, default status			90 days
Commercial and industrial
Financing receivable impaired
Carrying Value	105	66	$ 203	66
TDRs involving changes in the amount and/or timing of principal payments	73	33	73	33
TDRs involving changes in the amount and/or timing of interest payments	32	0	32	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	0	33	98	33
Carrying Value	323	118	323	118
TDR in payment default	7	0	7	0
Financial institutions
Financing receivable impaired
Carrying Value	0	1	0	1
TDR in payment default	0	1	0	1
Mortgage and real estate
Financing receivable impaired
Carrying Value	1	11	5	12
TDRs involving changes in the amount and/or timing of principal payments	0	1	0	2
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	1	10	5	10
Carrying Value	130	113	130	113
TDR in payment default	0	0	0	0
Other
Financing receivable impaired
Carrying Value	142		142
TDRs involving changes in the amount and/or timing of principal payments	0		0
TDRs involving changes in the amount and/or timing of interest payments	142		142
TDRs involving changes in the amount and/or timing of both principal and interest payments	0		0
Carrying Value	288	326	288	326
TDR in payment default	$ 0	$ 0	$ 0	$ 0