BUSINESS SEGMENTS (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($) country	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) country		Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)
Segment reporting information
Revenues, net of interest expense	$ 17,012	$ 17,760	$ 17,548	$ 17,555	$ 18,456	$ 18,692	$ 19,470	$ 19,736	$ 69,875	[1]	$ 76,354	[1]	$ 77,219	[1]
Provision for income taxes	1,509	1,733	1,723	1,479	1,403	1,881	2,036	2,120	6,444		7,440		7,197
Income (loss) from continuing operations	3,591	3,887	4,047	3,508	3,405	4,306	4,858	4,817	15,033		17,386		7,504
Identifiable assets	1,792,077				1,731,210				1,792,077		1,731,210
Provisions for credit losses and for benefits and claims	1,792	$ 1,736	$ 1,409	$ 2,045	2,514	$ 1,836	$ 1,648	$ 1,915	6,982		7,913		7,467
Operating Segments | Total Citicorp and Corporate/Other
Segment reporting information
Revenues, net of interest expense									66,023		67,394		67,911
Provision for income taxes									6,438		6,518		7,189
Income (loss) from continuing operations									14,427		16,401		10,974
Identifiable assets	1,738,000				1,650,000				1,738,000		1,650,000
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense									32,800		32,700		32,900
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense									10,000		10,000		9,500
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense									9,000		9,800		10,800
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense									13,800		14,000		14,400
Operating Segments | Global Consumer Banking(1)
Segment reporting information
Revenues, net of interest expense									31,763		32,495		34,296
Provision for income taxes									2,712		3,430		3,404
Income (loss) from continuing operations									5,108		6,376		6,702
Identifiable assets	$ 413,000				381,000				413,000		381,000
Provisions for credit losses and for benefits and claims									$ 6,400		5,500		5,500
Operating Segments | Institutional Clients Group
Segment reporting information
Number of countries where the entity provides a broad range of banking and financial products and services (over) | country	100								100
Revenues, net of interest expense									$ 33,850		33,991		33,312
Provision for income taxes									4,497		4,426		4,129
Income (loss) from continuing operations									9,928		9,529		9,645
Identifiable assets	$ 1,276,000				1,217,000				1,276,000		1,217,000
Provisions for credit losses and for benefits and claims									486		962		47
Operating Segments | Corporate/Other(1)
Segment reporting information
Revenues, net of interest expense									410		908		303
Provision for income taxes									(771)		(1,338)		(344)
Income (loss) from continuing operations									(609)		496		(5,373)
Identifiable assets	49,000				52,000				49,000		52,000
Operating Segments | Citi Holdings
Segment reporting information
Revenues, net of interest expense									3,852		8,960		9,308
Provision for income taxes									6		922		8
Income (loss) from continuing operations									606		985		(3,470)
Identifiable assets	$ 54,000				$ 81,000				54,000		81,000
Provisions for credit losses and for benefits and claims									$ 100		$ 1,500		$ 1,900

[1] Certain prior-period revenue and expense lines and totals were reclassified to conform to the current period’s presentation. See Note 3 to the Consolidated Financial Statements.