PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Principal transactions revenue
Principal transactions revenue	$ 2,640	$ 1,640	$ 5,087	$ 3,571
Interest rate contracts
Principal transactions revenue
Principal transactions revenue	1,647	1,071	3,129	1,862
Foreign exchange contracts
Principal transactions revenue
Principal transactions revenue	684	450	1,115	1,204
Equity contracts
Principal transactions revenue
Principal transactions revenue	222	4	380	346
Commodity and other contracts
Principal transactions revenue
Principal transactions revenue	91	84	207	63
Credit derivatives
Principal transactions revenue
Principal transactions revenue	(4)	31	256	96
Citicorp
Principal transactions revenue
Principal transactions revenue	2,627	1,549	5,111	3,601
Global Consumer Banking
Principal transactions revenue
Principal transactions revenue	243	159	454	415
Institutional Clients Group
Principal transactions revenue
Principal transactions revenue	2,407	1,434	4,822	3,350
Corporate/Other
Principal transactions revenue
Principal transactions revenue	(23)	(44)	(165)	(164)
Citi Holdings
Principal transactions revenue
Principal transactions revenue	13	91	(24)	(30)
Local Consumer Lending
Principal transactions revenue
Principal transactions revenue	(7)	(17)	(13)	(40)
Brokerage and Asset Management
Principal transactions revenue
Principal transactions revenue	(2)	(9)	(7)	(4)
Special Asset Pool
Principal transactions revenue
Principal transactions revenue	$ 22	$ 117	$ (4)	$ 14