BUSINESS SEGMENTS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment reporting information
Revenues, net of interest expense	$ 18,174	$ 13,951	$ 18,642	$ 19,406	$ 17,174	$ 20,831	$ 20,622	$ 19,726	$ 70,173	$ 78,353	$ 86,601
Provision (benefit) for income taxes	(206)	(1,488)	715	1,006	91	1,278	967	1,185	27	3,521	2,233
Income (loss) from continuing operations	1,336	524	2,987	3,062	998	3,742	3,332	3,031	7,909	11,103	10,951
Pretax provisions (credits) for credit losses and for benefits and claims	3,199	2,695	2,806	3,019	2,874	3,351	3,387	3,184	11,719	12,796	26,042
Total Citicorp and Corporate/Other
Segment reporting information
Revenues, net of interest expense									71,006	72,082	74,330
Provision (benefit) for income taxes									4,439	5,648	5,048
Income (loss) from continuing operations									14,469	15,206	15,384
Citicorp | North America
Segment reporting information
Revenues, net of interest expense									29,800	30,100	33,600
Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense									11,500	12,300	11,800
Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense									14,500	13,600	12,800
Citicorp | Asia
Segment reporting information
Revenues, net of interest expense									15,000	15,200	14,400
Global Consumer Banking
Segment reporting information
Regional business	4								4
Revenues, net of interest expense									40,214	39,195	39,369
Provision (benefit) for income taxes									3,733	3,509	1,551
Income (loss) from continuing operations									8,104	7,672	4,969
Pretax provisions (credits) for credit losses and for benefits and claims									6,600	6,600	14,000
Institutional Clients Group
Segment reporting information
Number of countries where the entity provides a broad range of banking and financial products and services	100								100
Revenues, net of interest expense									30,600	32,002	33,207
Provision (benefit) for income taxes									2,102	2,820	3,490
Income (loss) from continuing operations									7,990	8,262	10,173
Pretax provisions (credits) for credit losses and for benefits and claims									276	152	(82)
Corporate/Other
Segment reporting information
Revenues, net of interest expense									192	885	1,754
Provision (benefit) for income taxes									(1,396)	(681)	7
Income (loss) from continuing operations									(1,625)	(728)	242
Citi Holdings
Segment reporting information
Revenues, net of interest expense									(833)	6,271	12,271
Provision (benefit) for income taxes									(4,412)	(2,127)	(2,815)
Income (loss) from continuing operations									(6,560)	(4,103)	(4,433)
Pretax provisions (credits) for credit losses and for benefits and claims									$ 4,900	$ 6,000	$ 12,100