LOANS - Corporate Troubled Debt Restructurings (Details) - Corporate - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing receivable impaired
Carrying Value	$ 102	$ 1
TDRs involving changes in the amount and/or timing of principal payments	0	1
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	$ 102	0
Period within which default occurred post-modification (in years)	1 year
Number of days past due, default status	60 days
Carrying Value	$ 663	529
TDR in payment default	$ 0	0
Commercial banking loans
Financing receivable impaired
Number of days past due, default status	90 days
Commercial and industrial
Financing receivable impaired
Carrying Value	$ 98	0
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	0
TDRs involving changes in the amount and/or timing of both principal and interest payments	98	0
Carrying Value	219	88
TDR in payment default	0	0
Financial institutions
Financing receivable impaired
Carrying Value	2	0
TDR in payment default	0	0
Mortgage and real estate
Financing receivable impaired
Carrying Value	4	1
TDRs involving changes in the amount and/or timing of principal payments	0	1
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	4	0
Carrying Value	139	105
TDR in payment default	0	0
Other
Financing receivable impaired
Carrying Value	303	336
TDR in payment default	$ 0	$ 0