SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Asset-Backed Commercial Paper Conduits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Classification of Other Securitization Details
Commercial paper	$ 28,916	$ 20,222
Citi-administered asset-backed commercial paper conduits
Classification of Other Securitization Details
Purchased assets outstanding under conduits	21,300	21,100
Incremental funding commitments with clients	$ 16,700	$ 16,700
Weighted average life of commercial paper issued by conduits	82 days	68 days
Citi-administered asset-backed commercial paper conduits | Minimum
Classification of Other Securitization Details
Letters of credit as percentage of conduit assets	8.00%
Floor price of conduit's assets	$ 200
Citi-administered asset-backed commercial paper conduits | Maximum
Classification of Other Securitization Details
Letters of credit as percentage of conduit assets	10.00%
Floor price of conduit's assets	$ 350
Citi-administered asset-backed consolidated commercial paper conduits (ABCP)
Classification of Other Securitization Details
Letters of credit provided to conduits	2,100	$ 2,100
Commercial paper	$ 6,400	$ 10,100