GOODWILL AND INTANGIBLE ASSETS - Goodwill by Reporting Units (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Goodwill:
Goodwill	$ 22,575	$ 22,349
Operating Segments | Global Consumer Banking | Reporting units | North America Global Consumer Banking
Goodwill:
Goodwill	6,764
Operating Segments | Global Consumer Banking | Reporting units | Asia Global Consumer Banking
Goodwill:
Goodwill	4,895
Operating Segments | Global Consumer Banking | Reporting units | Latin America Global Consumer Banking
Goodwill:
Goodwill	1,220
Operating Segments | Institutional Clients Group | Reporting units | ICG—Banking
Goodwill:
Goodwill	3,091
Operating Segments | Institutional Clients Group | Reporting units | ICG—Markets and Securities Services
Goodwill:
Goodwill	6,536
Operating Segments | Citi Holdings | Reporting units | Citi Holdings—Consumer Latin America
Goodwill:
Goodwill	$ 69