GOODWILL AND INTANGIBLE ASSETS - Goodwill by Reporting Units (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 22, 2014
Goodwill:
Impairments	$ 0	$ 0	$ 0
Goodwill	23,592,000,000	25,009,000,000	25,673,000,000
Citi Holdings
Goodwill:
Goodwill	42,000,000	156,000,000	153,000,000
North America Global Consumer Banking
Goodwill:
Fair Value as a % of allocated book value	260.00%
Goodwill	6,756,000,000
EMEA Global Consumer Banking
Goodwill:
Fair Value as a % of allocated book value	178.00%
Goodwill	332,000,000
Asia Global Consumer Banking
Goodwill:
Fair Value as a % of allocated book value	264.00%
Goodwill	4,704,000,000
Latin America Global Consumer Banking
Goodwill:
Fair Value as a % of allocated book value	214.00%
Goodwill	1,602,000,000
Banking
Goodwill:
Fair Value as a % of allocated book value	404.00%
Goodwill	3,481,000,000
Markets and Securities Services
Goodwill:
Fair Value as a % of allocated book value	200.00%
Goodwill	6,675,000,000
Latin America Retirement Services
Goodwill:
Fair Value as a % of allocated book value	193.00%
Goodwill	$ 42,000,000
Spain Consumer Business | Citi Holdings
Goodwill:
Goodwill, Percentage Allocated To Sale				100.00%