DEBT - Short-Term Borrowings (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Short-Term Borrowings:
Commercial paper	$ 9,990	$ 16,155
Other borrowings	15,917	42,180
Total short-term borrowings	25,907	58,335
Collateralized short-term advances from Federal Home Loan Bank	1,000	11,200
Significant Citibank Entities
Short-Term Borrowings:
Commercial paper	9,990	16,085
Citigroup Inc.
Short-Term Borrowings:
Commercial paper	$ 0	$ 70