SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Asset-Backed Commercial Paper Conduits (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2023	Dec. 31, 2022
Classification of Other Securitization Details
Commercial paper	$ 22,843	$ 25,530
Citi-administered asset-backed commercial paper conduits
Classification of Other Securitization Details
Purchased assets outstanding under conduits	20,900	19,600
Incremental funding commitments with clients	$ 15,600	$ 13,900
Weighted average life of commercial paper issued by conduits	68 days	64 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	1,900	$ 1,900
Commercial paper	$ 9,900	$ 8,600

No definition available.

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- Definition

Represents the amount of floor price of asset-backed commercial paper conduits.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of incremental funding commitments with clients under conduits.

+ References

No definition available.

+ Details

Name:	c_IncrementalFundingCommitmentsWithClients
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the percentage of letters of credit to conduit assets.

+ References

No definition available.

+ Details

Name:	c_LettersOfCreditAsPercentageOfConduitAssets
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Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the letters of credit provided to conduits.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of purchased assets outstanding under conduits.

+ References

No definition available.

+ Details

Name:	c_PurchasedAssetsOutstandingUnderConduits
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the weighted average life, in days, of commercial paper issued by the conduits.

+ References

No definition available.

+ Details

Name:	c_WeightedAverageLifeOfCommercialPaperIssuedByConduits
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Data Type:	xbrli:durationItemType
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Period Type:	duration

- Definition

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(3))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Balance Type:	credit
Period Type:	instant

- Details

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- Details

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