DEBT - Short-Term Borrowings (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Short-Term Borrowings:
Commercial paper	$ 9,416.0	$ 16,155.0
Other borrowings	13,163.0	42,180.0
Total short-term borrowings	22,579.0	58,335.0
Collateralized short-term advances from Federal Home Loan Bank	1.9	11,200.0
Significant Citibank Entities
Short-Term Borrowings:
Commercial paper	9,416.0	16,085.0
Citigroup Inc.
Short-Term Borrowings:
Commercial paper	$ 0.0	$ 70.0