PRINCIPAL TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Principal transactions revenue
Principal transactions revenue	$ 1,101.0	$ 976.0	$ 6,188.0	$ 4,547.0
Interest rate contracts
Principal transactions revenue
Principal transactions revenue	451.0	427.0	3,580.0	2,289.0
Foreign exchange contracts
Principal transactions revenue
Principal transactions revenue	558.0	676.0	1,673.0	1,880.0
Equity contracts
Principal transactions revenue
Principal transactions revenue	27.0	(43.0)	407.0	303.0
Commodity and other contracts
Principal transactions revenue
Principal transactions revenue	16.0	8.0	223.0	71.0
Credit derivatives
Principal transactions revenue
Principal transactions revenue	49.0	(92.0)	305.0	4.0
Citicorp
Principal transactions revenue
Principal transactions revenue	1,078.0	990.0	6,189.0	4,591.0
Global Consumer Banking
Principal transactions revenue
Principal transactions revenue	209.0	204.0	663.0	619.0
Institutional Clients Group
Principal transactions revenue
Principal transactions revenue	814.0	731.0	5,636.0	4,081.0
Corporate/Other
Principal transactions revenue
Principal transactions revenue	55.0	55.0	(110.0)	(109.0)
Citi Holdings
Principal transactions revenue
Principal transactions revenue	$ 23.0	$ (14.0)	$ (1.0)	$ (44.0)