PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Principal transactions revenue.
Principal transactions revenue	$ 2,616	$ 2,362	$ 5,783	$ 6,478
Citicorp
Principal transactions revenue.
Principal transactions revenue	1,444	1,856	3,797	5,322
Regional Consumer Banking
Principal transactions revenue.
Principal transactions revenue	156	79	249	238
Institutional Clients Group
Principal transactions revenue.
Principal transactions revenue	1,288	1,777	3,548	5,084
Citi Holdings
Principal transactions revenue.
Principal transactions revenue	1,079	582	1,706	1,579
Local Consumer Lending
Principal transactions revenue.
Principal transactions revenue	(29)	(19)	(46)	(143)
Brokerage and Asset Management
Principal transactions revenue.
Principal transactions revenue	3	(2)	15	(28)
Special Asset Pool
Principal transactions revenue.
Principal transactions revenue	1,105	603	1,737	1,750
Corporate/Other
Principal transactions revenue.
Principal transactions revenue	93	(76)	280	(423)
Interest rate contracts
Principal transactions revenue.
Principal transactions revenue	1,722	2,376	3,346	3,750
Foreign exchange contracts
Principal transactions revenue.
Principal transactions revenue	595	262	1,382	503
Equity contracts
Principal transactions revenue.
Principal transactions revenue	147	(250)	575	315
Commodity and other contracts
Principal transactions revenue.
Principal transactions revenue	49	121	24	230
Credit derivatives
Principal transactions revenue.
Principal transactions revenue	$ 103	$ (147)	$ 456	$ 1,680