PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Principal transactions revenue.
Principal transactions revenue	$ 2,103	$ 2,085	$ 7,886	$ 8,563
Citicorp
Principal transactions revenue.
Principal transactions revenue	1,898	1,689	5,695	7,011
Regional Consumer Banking
Principal transactions revenue.
Principal transactions revenue	233	150	482	388
Institutional Clients Group
Principal transactions revenue.
Principal transactions revenue	1,665	1,539	5,213	6,623
Citi Holdings
Principal transactions revenue.
Principal transactions revenue	95	309	1,801	1,888
Local Consumer Lending
Principal transactions revenue.
Principal transactions revenue	(28)	(57)	(74)	(200)
Brokerage and Asset Management
Principal transactions revenue.
Principal transactions revenue	(14)	1	1	(27)
Special Asset Pool
Principal transactions revenue.
Principal transactions revenue	137	365	1,874	2,115
Corporate/Other
Principal transactions revenue.
Principal transactions revenue	110	87	390	(336)
Interest rate contracts
Principal transactions revenue.
Principal transactions revenue	1,972	633	5,318	4,383
Foreign exchange contracts
Principal transactions revenue.
Principal transactions revenue	576	992	1,958	1,495
Equity contracts
Principal transactions revenue.
Principal transactions revenue	(358)	468	217	783
Commodity and other contracts
Principal transactions revenue.
Principal transactions revenue	107	(33)	131	197
Credit derivatives
Principal transactions revenue.
Principal transactions revenue	$ (194)	$ 25	$ 262	$ 1,705