SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details 9) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Classification of Other Securitization Details
Commercial paper	$ 12,050,000,000	11,470,000,000
Trust assets	0
Citi-administered asset-backed commercial paper conduits (ABCP)
Classification of Other Securitization Details
Weighted average life of commercial paper issued by conduits	48 days	38 days
Commercial paper	0
Citi-administered asset-backed commercial paper conduits (ABCP) \| Minimum
Classification of Other Securitization Details
Weighted average life of commercial paper	25 days
Letters of credit as percentage of conduit assets	8.00%
Floor price of conduit's assets	200,000,000
Citi-administered asset-backed commercial paper conduits (ABCP) \| Maximum
Classification of Other Securitization Details
Weighted average life of commercial paper	50 days
Letters of credit as percentage of conduit assets	10.00%
Citi-administered asset-backed consolidated commercial paper conduits (ABCP)
Classification of Other Securitization Details
Letters of credit provided to conduits	2,000,000,000
Commercial paper	10,400,000,000
Citi-administered asset-backed unconsolidated commercial paper conduits (ABCP)
Classification of Other Securitization Details
Commercial paper	216,000,000
Notional exposure under program-wide liquidity agreement	600,000,000
Assets held by unconsolidated government guaranteed loan conduit	7,300,000,000
Municipal securities tender option bond trusts (TOBs)
Classification of Other Securitization Details
The threshold ownership percentage on Residual value of customers TOBs for which the reimbursement agreement applied	25.00%
Municipal bonds owned by trusts, that have credit guarantee provided by the Company	196,000,000
Liquidity agreements, customer TOB trust	4,600,000,000
Liquidity agreements, other trusts	6,500,000,000
Notional amount of offsetting reimbursement agreements	3,300,000,000
Floater inventory held by entity	$ 423,000,000

This element represents the amount of assets held in the unconsolidated government-guaranteed loan conduit.

No definition available.

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

- Details

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

- Definition

Represents the floater inventory related to the customer or proprietary TOB programs that is held by the entity.

+ References

No definition available.

+ Details

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

- 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

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

+ References

No definition available.

+ Details

Name:	c_LettersOfCreditAsPercentageOfConduitAssets
Namespace Prefix:	c_
Data Type:	num: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

This element represents the amount of liquidity agreements for customer TOB trusts.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of liquidity arrangements for other non-consolidated proprietary trusts.

+ References

No definition available.

+ Details

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

- Definition

This element represents the amount of municipal bonds owned by trusts that have a credit guarantee provided by the entity.

+ References

No definition available.

+ Details

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

- Definition

The notional amount of reimbursement agreements in place, which offset liquidity agreements for customer TOB trusts.

+ References

No definition available.

+ Details

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

- Definition

This element represents the notional exposure of loss under program wide liquidity arrangements.

+ References

No definition available.

+ Details

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

- Definition

Represent the threshold of ownership percentage on Residual value of customers TOBs in which if the customers own less than the threshold will have to reimburse the entity for any payment made under the liquidity arrangement.

+ References

No definition available.

+ Details

Name:	c_TheThresholdOwnershipPercentageOnResidualValueByCustomerTOBInWhichReimbursementAgreementApplied
Namespace Prefix:	c_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the weighted average life, in days, of short-term commercial paper.

+ References

No definition available.

+ Details

Name:	c_WeightedAverageLifeOfCommercialPaper
Namespace Prefix:	c_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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
Namespace Prefix:	c_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(b))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 61

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 17

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_AssetsHeldInTrust
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a(3)

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13

-Subparagraph 2

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a)(3))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(2))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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