BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment reporting information
Revenues, net of interest expense	$ 20,731	$ 18,576
Provision (benefits) for income taxes	576	1,275
Income (loss) from continuing operations	2,534	4,737
Identifiable assets	2,219,770		$ 1,951,158
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense	10,200	8,300
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense	3,500	3,200
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense	2,600	2,500
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense	4,400	4,100
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense	8,174	8,090
Provision (benefits) for income taxes	(270)	381
Income (loss) from continuing operations	(755)	1,320
Identifiable assets	403,000		407,000
Provisions for credit losses and for benefits and claims	4,800	2,000
Operating Segments | Institutional Clients Group
Segment reporting information
Revenues, net of interest expense	12,484	10,018
Provision (benefits) for income taxes	1,044	955
Income (loss) from continuing operations	3,626	3,412
Identifiable assets	1,723,000		1,447,000
Provisions for credit losses and for benefits and claims	2,004	32
Corporate/Other
Segment reporting information
Revenues, net of interest expense	73	468
Provision (benefits) for income taxes	(198)	(61)
Income (loss) from continuing operations	(337)	5
Identifiable assets	94,000		$ 97,000
Provisions for credit losses and for benefits and claims	$ 192	$ (25)