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

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 increase (decrease) in the amount of assets due to consolidation of loan because of changes in the primary risks and design of the conduit.

+ References

No definition available.

+ Details

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

- Definition

Represents increase (decrease) in the amount of liabilities due to consolidation of loan because of changes in the primary risks and design of the conduit.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	c_IncrementalFundingCommitmentsWithClients
Namespace Prefix:	c_
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
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

Represents number of consolidated conduit which holds only loans that are fully guaranteed primarily by AAA rated government agencies that support export and development financing programs.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of purchased assets outstanding under conduits.

+ References

No definition available.

+ Details

Name:	c_PurchasedAssetsOutstandingUnderConduits
Namespace Prefix:	c_
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
Namespace Prefix:	c_
Data Type:	xbrli:durationItemType
Balance Type:	na
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 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 3: 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

Reference 4: 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 5: 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

- Definition

Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.4)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 4

-Article 7

+ Details

Name:	us-gaap_OtherIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=c_EntityAdministeredAssetBackedCommercialPaperConduitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=c_EntityConsolidatedAdministeredAssetBackedCommercialPaperConduitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Asset-Backed Commercial Paper Conduits (Details) (USD $)	12 Months Ended		3 Months Ended
	Dec. 31, 2014 conduit	Dec. 31, 2013	Jun. 30, 2013
Classification of Other Securitization Details
Commercial paper	$ 16,155,000,000us-gaap_CommercialPaper	$ 17,878,000,000us-gaap_CommercialPaper
Citi-administered asset-backed commercial paper conduits (ABCP)
Classification of Other Securitization Details
Purchased assets outstanding under conduits	29,200,000,000	31,800,000,000
Incremental funding commitments with clients	15,300,000,000	13,500,000,000
Weighted average life of commercial paper issued by conduits	57 days	67 days
Number of conduit which holds only loans that are fully guaranteed primarily by AAA-rated government agencies	1
Citi-administered asset-backed commercial paper conduits (ABCP) \| Minimum
Classification of Other Securitization Details
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
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	2,300,000,000	2,300,000,000
Commercial paper	10,600,000,000	13,900,000,000
Increase in the amount of assets due to consolidation of loan because of changes in the primary risks and design of the conduit		7,000,000,000
Increase in the amount of liabilities due to consolidation of loan because of changes in the primary risks and design of the conduit	7,000,000,000
Net pretax gain due to consolidation of loan because of changes in the primary risks and design of the conduit			$ 40,000,000