LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financing receivable impaired
Carrying Value	$ 124	$ 48	$ 475	$ 126
TDRs involving changes in the amount and/or timing of principal payments	114	13	187	48
TDRs involving changes in the amount and/or timing of interest payments	2	0	176	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	8	35	$ 112	78
Period within which default occurred post-modification			1 year
Number of days past due, default status			60 days
Carrying Value	775	587	$ 775	587
TDR in payment default	0	0	7	1
Commercial and industrial
Financing receivable impaired
Carrying Value	112	13	316	79
TDRs involving changes in the amount and/or timing of principal payments	103	12	176	45
TDRs involving changes in the amount and/or timing of interest payments	2	0	34	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	7	1	106	34
Carrying Value	394	126	394	126
TDR in payment default	0	0	7	0
Financial institutions
Financing receivable impaired
Carrying Value	10		10
TDRs involving changes in the amount and/or timing of principal payments	10		10
TDRs involving changes in the amount and/or timing of interest payments	0		0
TDRs involving changes in the amount and/or timing of both principal and interest payments	0		0
Carrying Value	10	1	10	1
TDR in payment default	0	0	0	1
Mortgage and real estate
Financing receivable impaired
Carrying Value	2	35	7	47
TDRs involving changes in the amount and/or timing of principal payments	1	1	1	3
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	34	6	44
Carrying Value	80	144	80	144
TDR in payment default	0	0	0	0
Other
Financing receivable impaired
Carrying Value	0		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	0		142
TDRs involving changes in the amount and/or timing of both principal and interest payments	0		0
Carrying Value	291	316	291	316
TDR in payment default	$ 0	$ 0	$ 0	$ 0
Commercial banking loans
Financing receivable impaired
Number of days past due, default status			90 days