BUSINESS SEGMENTS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment reporting information
Revenues, net of interest expense	$ 17,812	$ 19,604	$ 19,342	$ 20,124	$ 17,779	$ 17,904	$ 20,488	$ 20,248	$ 76,882	[1]	$ 76,419	[1]	$ 69,190
Provision for income taxes	991	1,985	1,838	2,050	1,090	1,080	2,127	1,570	6,864		5,867		7
Income (loss) from continuing operations	382	2,914	253	3,951	2,324	3,186	4,188	3,931	7,500		13,630		7,818
Identifiable assets	1,842,530				1,880,382				1,842,530		1,880,382
Provisions for credit losses and for benefits and claims	2,013	1,750	1,730	1,974	2,072	1,959	2,024	2,459	7,467		8,514		11,329
Citicorp | North America
Segment reporting information
Revenues, net of interest expense									32,000		31,200		29,900
Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense									10,900		11,500		11,500
Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense									13,400		14,000		13,500
Citicorp | Asia
Segment reporting information
Revenues, net of interest expense									14,700		15,000		15,000
Global Consumer Banking
Segment reporting information
Regional business	4								4
Provisions for credit losses and for benefits and claims									6,100		6,800		6,200
Institutional Clients Group
Segment reporting information
Number of countries where the entity provides a broad range of banking and financial products and services	100								100
Provisions for credit losses and for benefits and claims									57		78		276
Citi Holdings
Segment reporting information
Provisions for credit losses and for benefits and claims									1,300		1,600		4,900
Operating Segments | Total Citicorp and Corporate/Other
Segment reporting information
Revenues, net of interest expense									71,067		71,853		69,995
Provision for income taxes									6,743		6,999		4,396
Income (loss) from continuing operations									10,866		15,547		14,383
Identifiable assets	1,745,000				1,763,000				1,745,000		1,763,000
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense									37,753		38,165		39,105
Provision for income taxes									3,473		3,424		3,468
Income (loss) from continuing operations									6,938		6,763		7,597
Identifiable assets	396,000				405,000				396,000		405,000
Operating Segments | Institutional Clients Group
Segment reporting information
Revenues, net of interest expense									33,267		33,567		30,762
Provision for income taxes									3,729		3,857		2,021
Income (loss) from continuing operations									9,521		9,414		7,834
Identifiable assets	1,020,000				1,045,000				1,020,000		1,045,000
Operating Segments | Corporate/Other
Segment reporting information
Revenues, net of interest expense									47		121		128
Provision for income taxes									(459)		(282)		(1,093)
Income (loss) from continuing operations									(5,593)		(630)		(1,048)
Identifiable assets	329,000				313,000				329,000		313,000
Operating Segments | Citi Holdings
Segment reporting information
Revenues, net of interest expense									5,815		4,566		(805)
Provision for income taxes									121		(1,132)		(4,389)
Income (loss) from continuing operations									(3,366)		(1,917)		(6,565)
Identifiable assets	$ 98,000				$ 117,000				$ 98,000		$ 117,000

[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.