GOODWILL AND INTANGIBLE ASSETS - Goodwill by Reporting Units (Details) (USD $)	3 Months Ended		12 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2012	Jan. 01, 2015	Dec. 31, 2014
Goodwill:
Impairments	$ 16,000,000	$ 0	$ 0
Goodwill	23,150,000,000				23,592,000,000
North America Global Consumer Banking
Goodwill:
Goodwill	6,725,000,000
EMEA Global Consumer Banking
Goodwill:
Goodwill	293,000,000
Asia Global Consumer Banking
Goodwill:
Goodwill	4,626,000,000
Latin America Global Consumer Banking
Goodwill:
Goodwill	1,465,000,000
Banking
Goodwill:
Goodwill	3,372,000,000
Markets and Securities Services
Goodwill:
Goodwill	6,569,000,000
Latin America Retirement Services
Goodwill:
Goodwill	0
Goodwill, reclassified to other assets held-for-sale	42,000,000
Citi Holdings—Consumer EMEA
Goodwill:
Fair Value as a % of allocated book value				107.00%
Goodwill	23,000,000
Citi Holdings — Consumer Japan
Goodwill:
Goodwill	0
Goodwill, reclassified to other assets held-for-sale	61,000,000
Citi Holdings—Consumer Latin America
Goodwill:
Goodwill	77,000,000
Consumer Finance South Korea
Goodwill:
Impairments	$ 16,000,000