DEBT - Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Instrument
Long-term debt, at fair value	$ 257,425	$ 254,374
Trust preferred securities	1,600	1,700
Citigroup Inc.
Debt Instrument
Long-term debt, at fair value	167,874	164,945
Bank
Debt Instrument
Long-term debt, at fair value	18,799	23,567
Bank \| Senior notes
Debt Instrument
Collateralized long-term advances from Federal Home Loan Bank	2,300	5,300
Broker-dealer and other
Debt Instrument
Long-term debt, at fair value	$ 70,752	$ 65,862

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant