BUSINESS SEGMENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment reporting information
Revenues, net of interest expense	$ 18,120	$ 17,555
Provision (benefits) for income taxes	1,863	1,479
Income (loss) from continuing operations	4,118	3,508
Identifiable assets	1,821,635		$ 1,792,077
Provisions for credit losses and for benefits and claims	1,662	2,045
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense	8,300	7,800
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense	2,800	2,200
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense	2,300	2,200
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense	3,500	3,400
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense	7,817	7,714
Provision (benefits) for income taxes	584	634
Income (loss) from continuing operations	1,003	1,194
Identifiable assets	412,000		412,000
Provisions for credit losses and for benefits and claims	1,800	1,500
Operating Segments | Institutional Clients Group
Segment reporting information
Revenues, net of interest expense	9,126	7,895
Provision (benefits) for income taxes	1,375	764
Income (loss) from continuing operations	3,011	1,869
Identifiable assets	1,314,000		1,277,000
Provisions for credit losses and for benefits and claims	(205)	390
Operating Segments | Corporate/Other
Segment reporting information
Revenues, net of interest expense	1,177	1,946
Provision (benefits) for income taxes	(96)	81
Income (loss) from continuing operations	104	445
Identifiable assets	96,000		$ 103,000
Provisions for credit losses and for benefits and claims	$ 52	$ 170