BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment reporting information
Revenues, net of interest expense	$ 17,901	$ 17,548	$ 36,021	$ 35,103
Provision (benefits) for income taxes	1,795	1,723	3,658	3,202
Income (loss) from continuing operations	3,883	4,047	8,001	7,555
Identifiable assets	1,864,063		1,864,063		$ 1,792,077
Provisions for credit losses and for benefits and claims	1,717	1,409	3,379	3,454
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense	8,500	8,100	17,000	16,000
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense	2,800	2,600	5,600	4,700
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense	2,300	2,300	4,600	4,400
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense	3,600	3,400	7,000	6,900
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense	8,035	7,674	15,852	15,388
Provision (benefits) for income taxes	647	667	1,231	1,301
Income (loss) from continuing operations	1,129	1,285	2,132	2,479
Identifiable assets	419,000		419,000		412,000
Provisions for credit losses and for benefits and claims	1,800	1,400	3,600	2,900
Operating Segments | Institutional Clients Group
Segment reporting information
Revenues, net of interest expense	9,213	8,689	18,339	16,584
Provision (benefits) for income taxes	1,327	1,229	2,702	1,993
Income (loss) from continuing operations	2,780	2,615	5,791	4,484
Identifiable assets	1,353,000		1,353,000		1,277,000
Provisions for credit losses and for benefits and claims	87	82	(118)	472
Operating Segments | Corporate/Other
Segment reporting information
Revenues, net of interest expense	653	1,185	1,830	3,131
Provision (benefits) for income taxes	(179)	(173)	(275)	(92)
Income (loss) from continuing operations	(26)	147	78	592
Identifiable assets	92,000		92,000		$ 103,000
Provisions for credit losses and for benefits and claims	$ (132)	$ (98)	$ (80)	$ 72