PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Principal transactions revenue
Principal transactions revenue	$ 976	$ 2,103	$ 4,547	$ 7,886
Interest rate contracts
Principal transactions revenue
Principal transactions revenue	427	1,972	2,289	5,318
Foreign exchange contracts
Principal transactions revenue
Principal transactions revenue	676	576	1,880	1,958
Equity contracts
Principal transactions revenue
Principal transactions revenue	(43)	(358)	303	217
Commodity and other contracts
Principal transactions revenue
Principal transactions revenue	8	107	71	131
Credit derivatives
Principal transactions revenue
Principal transactions revenue	(92)	(194)	4	262
Citicorp
Principal transactions revenue
Principal transactions revenue	935	1,898	4,700	5,695
Global Consumer Banking
Principal transactions revenue
Principal transactions revenue	204	233	619	482
Institutional Clients Group
Principal transactions revenue
Principal transactions revenue	731	1,665	4,081	5,213
Citi Holdings
Principal transactions revenue
Principal transactions revenue	(14)	95	(44)	1,801
Local Consumer Lending
Principal transactions revenue
Principal transactions revenue	(16)	(28)	(56)	(74)
Brokerage and Asset Management
Principal transactions revenue
Principal transactions revenue	3	(14)	(1)	1
Special Asset Pool
Principal transactions revenue
Principal transactions revenue	(1)	137	13	1,874
Corporate/Other
Principal transactions revenue
Principal transactions revenue	$ 55	$ 110	$ (109)	$ 390