PRINCIPAL TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Principal transactions revenue
Principal transactions revenue	$ 2,562	$ 1,816	$ 5,584	$ 3,656
Interest rate risks
Principal transactions revenue
Principal transactions revenue	1,411	1,140	3,177	1,947
Foreign exchange risks
Principal transactions revenue
Principal transactions revenue	802	402	1,390	1,015
Equity risks
Principal transactions revenue
Principal transactions revenue	58	(55)	246	(5)
Commodity and other risks
Principal transactions revenue
Principal transactions revenue	148	121	238	265
Credit products and risks
Principal transactions revenue
Principal transactions revenue	143	208	533	434
Citicorp | Operating Segments
Principal transactions revenue
Principal transactions revenue	2,562	1,816	5,584	3,656
Global Consumer Banking | Operating Segments
Principal transactions revenue
Principal transactions revenue	142	165	291	308
Institutional Clients Group | Operating Segments
Principal transactions revenue
Principal transactions revenue	2,079	1,911	4,747	3,487
Corporate/Other | Operating Segments
Principal transactions revenue
Principal transactions revenue	$ 341	$ (260)	$ 546	$ (139)