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

Represents the amount of cash initial margin collected and remitted.

No definition available.

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

Represents the amount of compensation received for standard representations and warranties.

No definition available.

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

- References

No definition available.

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

Represents the maximum potential payments with respect to the entity's guarantees that expire after one year.

No definition available.

Name:	c_GuaranteeObligationsMaximumExposureExpireAfterOneYear
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the maximum potential payments with respect to the entity's guarantees that expire within one year.

No definition available.

Name:	c_GuaranteeObligationsMaximumExposureExpireWithinOneYear
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Guarantor Obligations, Maximum Exposure, Undiscounted, Required Disclosure

No definition available.

Name:	c_GuarantorObligationsMaximumExposureUndiscountedRequiredDisclosure
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the letters of credit in favor of the entity held as collateral to reimburse losses realized under the guarantees.

No definition available.

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

Represents the liability recorded in the balance sheet related to long-term care insurance indemnification.

No definition available.

Name:	c_LongTermCareInsuranceIndemnificationLiability
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

This element represents the number of trusts funded by the reinsurer.

No definition available.

Name:	c_NumberOfTrustFundedByReinsurer
Namespace Prefix:	c_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of types of margin.

No definition available.

Name:	c_NumberOfTypesOfMargin
Namespace Prefix:	c_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

This element represents the repurchase reserve created for consumer mortgages, representations and warranties.

No definition available.

Name:	c_RepurchaseReserveConsumerMortgagesRepresentationsAndWarranties
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Securities and Other Marketable Assets Held as Collateral

No definition available.

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

Represents the stated or notional amounts included in the indemnification clauses.

No definition available.

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

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingNonInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ExternalCreditRatingByGroupingAxis=c_ExternalCreditRatingNotRatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialStandbyLetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_PerformanceGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_DerivativeInstrumentsConsideredGuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_LoansSoldWithRecourseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_SecuritiesLendingIndemnificationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_CreditCardMerchantProcessingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_CreditCardArrangementswithPartnersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_GuarantorObligationsOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_GuaranteeObligationsByNatureAxis=c_FuturesAndOverTheCounterDerivativesClearingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: