SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details 9) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Classification of Other Securitization Details
Commercial paper	$ 23,644,000,000	24,657,000,000
Citi-administered asset-backed commercial paper conduits (ABCP)
Classification of Other Securitization Details
Weighted average life of commercial paper, low end of range (in days)	30
Weighted average life of commercial paper, high end of range (in days)	60
Weighted average life of commercial paper issued by conduits (in days)	40	41
Letters of credit as percentage of conduit assets, low end of range (as a percent)	8.00%
Letters of credit as percentage of conduit assets, high end of range (as a percent)	10.00%
Floor price of conduit's assets	200,000,000
Letters of credit provided to conduits	1,800,000,000
Notional exposure under program-wide liquidity agreement	600,000,000
Assets held by unconsolidated government guaranteed loan conduit	9,500,000,000
Third-party commercial paper conduits
Classification of Other Securitization Details
Notional amount of commercial paper under third party conduits	764,000,000
Amount funded under liquidity facilities	466,000,000
Collateralized debt obligations (CDOs)
Classification of Other Securitization Details
Commercial paper issuance, description of variable rate basis	LIBOR
Commercial paper issuance, limit on LIBOR variable rate, low end (in basis points)	35
Commercial paper issuance, limit on LIBOR variable rate, high end (in basis points)	40
Municipal securities tender option bond trusts (TOBs)
Classification of Other Securitization Details
Percentage of maximum residuals to total trust funding (as a percent)	25.00%
Floater inventory held by entity	76,000,000
Municipal bonds owned by trusts, that have credit guarantee provided by the Company	300,000,000
Percentage of residuals to trust capital structure, for determining reimbursement agreement with residual holder (as a percent)	1.00%
Proceeds from new securitizations	100,000,000
Liquidity agreements, customer TOB trust	9,700,000,000
Percentage of minimum residual owned by customer to bond value, remaining exposure (as a percent)	25.00%
Notional amount of offsetting reimbursement agreements	8,300,000,000
Notional amount to QSPE TOB trusts and other non-consolidated proprietary TOB trusts	20,000,000
Residuals held by hedge funds, consolidated and managed, proprietary TOB trusts	$ 76,000,000

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

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

The reference rate for the specified maximum variable rate of interest related to the issuance of commercial paper under the terms of the liquidity puts.

+ Details

Name:	c_CommercialPaperIssuanceDescriptionOfVariableRateBasis
Namespace Prefix:	c
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The high end of the range of basis points added to the reference rate to compute the specified maximum variable rate of interest related to the issuance of commercial paper under the terms of the liquidity puts.

+ Details

Name:	c_CommercialPaperIssuanceLimitOnLIBORVariableRateHighEndOfRange
Namespace Prefix:	c
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The low end of the range of basis points added to the reference rate to compute the specified maximum variable rate of interest related to the issuance of commercial paper under the terms of the liquidity puts.

+ Details

Name:	c_CommercialPaperIssuanceLimitOnLIBORVariableRateLowEndOfRange
Namespace Prefix:	c
Data Type:	xbrli:decimalItemType
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 .

+ 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.

+ Details

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

- Definition

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

+ Details

Name:	c_LettersOfCreditAsPercentageOfConduitAssetsHighEndOfRange
Namespace Prefix:	c
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

Name:	c_LettersOfCreditAsPercentageOfConduitAssetsLowEndOfRange
Namespace Prefix:	c
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the letters of credit provided to conduits.

+ 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.

+ Details

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

- Definition

This element represents the amount funded under the liquidity facilities.

+ Details

Name:	c_LiquidityFacilitiesAmountFunded
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ Details

Name:	c_MaximumExposureOfLossUnderProgramWideLiquidityArrangements
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the percentage by which residuals are frequently less than the trust's total funding.

+ Details

Name:	c_MaximumPercentageOfJuniorResidualSecuritiesToTotalTrustfunding
Namespace Prefix:	c
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

Name:	c_MuncipalBondsOwnedByTrustWithCreditGuarantee
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the notional amount of liquidity arrangements for other non-consolidated proprietary trusts.

+ Details

Name:	c_NotionalAmountLiquidityArrangementsOther
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the notional amount of commercial paper issued under third party conduits.

+ Details

Name:	c_NotionalAmountOfCommercialPaperUnderThirdPartyConduits
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.

+ Details

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

- Definition

The percentage of residual owned by the customer to the bond value, related to the remaining exposure with respect to customer TOB trusts.

+ Details

Name:	c_PercentageOfResidualOwnedByCustomerToBondValue
Namespace Prefix:	c
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage whereby if the customer TOB's residual is less than this specified percentage of the trust's capital structure, the entity has a reimbursement agreement with the residual holder.

+ Details

Name:	c_PercentageOfResidualsToTrustsCapitalStructureInCustomerTOB
Namespace Prefix:	c
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of assets in proprietary TOB trusts where the residuals are held by hedge funds that are consolidated and managed by the entity.

+ Details

Name:	c_ResidualsHeldByHedgeFundsInProprietaryTOBTrust
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ Details

Name:	c_WeightedAverageLifeOfCommercialPaperHighEndOfRange
Namespace Prefix:	c
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

Name:	c_WeightedAverageLifeOfCommercialPaperIssuedByConduits
Namespace Prefix:	c
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ Details

Name:	c_WeightedAverageLifeOfCommercialPaperLowEndOfRange
Namespace Prefix:	c
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of proceeds from new securitizations or asset-backed financing arrangements during this reporting period for this class of securitization or asset-backed financing arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph a(3)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph h(4)

+ Details

Name:	us-gaap_CashFlowsBetweenSecuritizationSpecialPurposeEntitySPEAndTransferorProceedsFromNewlySecuritizedAssets
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 7

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 13
-Subparagraph 2
-Article 9

+ Details

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