PRINCIPAL TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Principal transactions revenue
Principal transactions revenue	$ 2,238	$ 1,327	$ 5,894	$ 5,471
Interest rate risks
Principal transactions revenue
Principal transactions revenue	1,282	907	3,229	3,497
Foreign exchange risks
Principal transactions revenue
Principal transactions revenue	466	432	1,481	1,236
Equity risks
Principal transactions revenue
Principal transactions revenue	81	(183)	76	(254)
Commodity and other risks
Principal transactions revenue
Principal transactions revenue	171	180	436	614
Credit products and risks
Principal transactions revenue
Principal transactions revenue	238	(9)	672	378
Citicorp | Operating Segments
Principal transactions revenue
Principal transactions revenue	2,189	1,327	5,838	5,378
Global Consumer Banking | Operating Segments
Principal transactions revenue
Principal transactions revenue	163	144	473	444
Institutional Clients Group | Operating Segments
Principal transactions revenue
Principal transactions revenue	2,063	1,209	5,548	5,199
Corporate/Other | Operating Segments
Principal transactions revenue
Principal transactions revenue	(37)	(26)	(183)	(265)
Citi Holdings | Operating Segments
Principal transactions revenue
Principal transactions revenue	$ 49	$ 0	$ 56	$ 93