LOANS (Details 9) (Corporate, USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Financing receivable impaired
Carrying Value	$ 78	$ 227
TDRs involving changes in the amount and/or timing of principal payments	77	2
TDRs involving changes in the amount and/or timing of both principal and interest payments	1	225
Balance of principal forgiven or deferred		3
Net P&L Impact	1	37
Carrying Value	963	1,403
Commercial and industrial
Financing receivable impaired
Carrying Value	17
TDRs involving changes in the amount and/or timing of principal payments	17
Net P&L Impact	1
Carrying Value	272	412
Loans to financial institutions
Financing receivable impaired
Carrying Value	551	375
Mortgage and real estate
Financing receivable impaired
Carrying Value	61	227
TDRs involving changes in the amount and/or timing of principal payments	60	2
TDRs involving changes in the amount and/or timing of both principal and interest payments	1	225
Balance of principal forgiven or deferred		3
Net P&L Impact		37
Carrying Value	120	583
Other
Financing receivable impaired
Carrying Value	$ 20	$ 33

Represents the amount of financing receivables' principal forgiven by the holder of the instrument.

No definition available.

Name:	c_FinancingReceivablesPrincipalForgiven
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Represents the carrying value of loans receivable modified in a troubled debt restructuring during the current year.

No definition available.

Name:	c_FinancingReceivablesTroubledDebtRestructuringCarryingValue
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
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Represents the amount of troubled debt restructurings on net profit and loss.

No definition available.

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

Represents the amount of troubled debt restructurings involving changes in the amount or timing of principal and interest payments.

No definition available.

Name:	c_FinancingReceivablesTroubledDebtRestructuringInvolvingChangeInAmountOrTimingOfPrincipalInterestPayment
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Represents the amount of troubled debt restructurings involving changes in the amount or timing of principal payments.

No definition available.

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

Represents the carrying value of loans receivable modified in a troubled debt restructuring during the current year.

No definition available.

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

Name:	us-gaap_FinancingReceivableImpairedLineItems
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Balance Type:	na
Period Type:	duration