BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment reporting information
Revenues, net of interest expense	$ 17,760	$ 18,692	$ 52,863	$ 57,898
Provision for income taxes	1,733	1,881	4,935	6,037
Income (loss) from continuing operations	3,887	4,306	11,442	13,981
Identifiable assets	1,818,117		1,818,117		$ 1,731,210
Provisions for credit losses and for benefits and claims	1,736	1,836	5,190	5,399
Operating Segments | Total Citicorp and Corporate/Other
Segment reporting information
Revenues, net of interest expense	16,883	17,011	49,668	52,103
Provision for income taxes	1,773	1,816	4,860	5,683
Income (loss) from continuing operations	3,813	4,307	10,923	13,676
Identifiable assets	1,757,000		1,757,000		1,650,000
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense	8,500	8,300	24,500	25,100
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense	2,600	2,400	7,400	7,900
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense	2,300	2,600	6,800	7,500
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense	3,500	3,500	10,500	10,800
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense	8,227	8,134	23,730	24,620
Provision for income taxes	690	932	2,017	2,660
Income (loss) from continuing operations	1,288	1,691	3,842	5,014
Identifiable assets	412,000		412,000		381,000
Provisions for credit losses and for benefits and claims	1,800	1,300	4,700	4,100
Operating Segments | Institutional Clients Group
Segment reporting information
Revenues, net of interest expense	8,628	8,659	25,510	26,682
Provision for income taxes	1,266	1,198	3,373	3,894
Income (loss) from continuing operations	2,772	2,433	7,446	8,267
Identifiable assets	1,302,000		1,302,000		1,217,000
Provisions for credit losses and for benefits and claims	(90)	313	382	312
Operating Segments | Corporate/Other
Segment reporting information
Revenues, net of interest expense	28	218	428	801
Provision for income taxes	(183)	(314)	(530)	(871)
Income (loss) from continuing operations	(247)	183	(365)	395
Identifiable assets	43,000		43,000		52,000
Operating Segments | Citi Holdings
Segment reporting information
Revenues, net of interest expense	877	1,681	3,195	5,795
Provision for income taxes	(40)	65	75	354
Income (loss) from continuing operations	74	(1)	519	305
Identifiable assets	61,000		61,000		$ 81,000
Provisions for credit losses and for benefits and claims	$ 0	$ 200	$ 100	$ 1,000