SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Funding, Liquidity Facilities and Subordinated Interests (Details) - USD ($) $ in Billions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Citibank Credit Card Master Trust (Master Trust)
Funding, Liquidity Facilities and Subordinated Interests
Weighted average maturity of term notes	2 years 9 months 18 days	3 years 1 month 6 days
Term notes issued to third parties	$ 18.2	$ 18.2
Term notes retained by Citigroup affiliates	3.5	4.3
Total Master Trust liabilities	$ 21.7	$ 22.5
Citibank OMNI Master Trust (Omni Trust)
Funding, Liquidity Facilities and Subordinated Interests
Weighted average maturity of term notes	1 year 4 months 24 days	1 year 7 months 6 days
Term notes issued to third parties	$ 1.5	$ 1.5
Term notes retained by Citigroup affiliates	1.9	1.9
Total Master Trust liabilities	$ 3.4	$ 3.4