PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Principal transactions revenue
Principal transactions revenue	$ 1,640	$ 2,616	$ 3,571	$ 5,783
Interest rate contracts
Principal transactions revenue
Principal transactions revenue	1,071	1,722	1,862	3,346
Foreign exchange contracts
Principal transactions revenue
Principal transactions revenue	450	595	1,204	1,382
Equity contracts
Principal transactions revenue
Principal transactions revenue	4	147	346	575
Commodity and other contracts
Principal transactions revenue
Principal transactions revenue	84	49	63	24
Credit derivatives
Principal transactions revenue
Principal transactions revenue	31	103	96	456
Citicorp
Principal transactions revenue
Principal transactions revenue	1,593	1,444	3,765	3,797
Global Consumer Banking
Principal transactions revenue
Principal transactions revenue	159	156	415	249
Institutional Clients Group
Principal transactions revenue
Principal transactions revenue	1,434	1,288	3,350	3,548
Citi Holdings
Principal transactions revenue
Principal transactions revenue	91	1,079	(30)	1,706
Local Consumer Lending
Principal transactions revenue
Principal transactions revenue	(17)	(29)	(40)	(46)
Brokerage and Asset Management
Principal transactions revenue
Principal transactions revenue	(9)	3	(4)	15
Special Asset Pool
Principal transactions revenue
Principal transactions revenue	117	1,105	14	1,737
Corporate/Other
Principal transactions revenue
Principal transactions revenue	$ (44)	$ 93	$ (164)	$ 280