SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Credit Card Securitizations (Details) $ in Billions	3 Months Ended
Mar. 31, 2023 USD ($) trust	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Securitized credit card receivables
Number of trusts to hold securitized credit card receivables \| trust	2
Ownership interests in principal amount of trust credit card receivables
Sold to investors via trust-issued securities	$ 6.9		$ 7.9
Retained by Citigroup as trust-issued securities	6.4		6.4
Retained by Citigroup via non-certificated interests	18.8		19.5
Total ownership interests in principal amount of trust credit card receivables	32.1		$ 33.8
Credit card securitizations
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	0.0	$ 0.0
Pay down of maturing notes	$ (1.0)	$ 0.0

No definition available.

Name:	c_OwnershipInterestsInPrincipalAmountOfTrustCreditCardReceivablesAbstract
Namespace Prefix:	c_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The payment of maturing notes related to securitizations.

+ References

No definition available.

+ Details

Name:	c_PaymentOfMaturingNotesSecuritizations
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the ownership interests in principal amount of trust credit card receivables sold to investors via trust-issued securities.

+ References

No definition available.

+ Details

Name:	c_PortionOfPrincipalAmountOutstandingOfSecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherSoldToInvestorsViaTrustCreditCardReceivables
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the ownership interests in principal amount of trust credit card receivables retained by the reporting entity via non-certificated interests.

+ References

No definition available.

+ Details

Name:	c_PortionOfSecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherRetainedByReportingEntityViaNonCertificatedInterests
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the ownership interests in principal amount of trust credit card receivables retained by the reporting entity as trust-issued securities.

+ References

No definition available.

+ Details

Name:	c_PortionOfSecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherRetainedByTrustIssuedSecurities
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the number of securitization trusts established to hold in trust a specific type of securitized receivables.

+ References

No definition available.

+ Details

Name:	c_SecuritizationTrustNumber
Namespace Prefix:	c_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	c_SecuritizedCreditCardReceivablesLineItems
Namespace Prefix:	c_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the principal amount of credit card receivables held in trusts.

+ References

No definition available.

+ Details

Name:	c_SecuritizedCreditCardReceivablesPrincipalAmountOutstanding
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_CashFlowsBetweenTransfereeAndTransferorAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(1)
-URI https://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

+ Details

Name:	us-gaap_CashFlowsBetweenTransfereeAndTransferorProceedsFromNewTransfers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedCreditCardSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: