Carrying amount of certain credit related trading assets as of the balance sheet date for which the fair value option was elected.

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

- Details

Name:	c_FairValueElectionsDisclosureAbstract
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Balance Type:	na
Period Type:	duration

- Definition

For short-term borrowings which the fair value option has been elected, this item represents the amount by which the aggregate fair value exceeds the aggregate unpaid principal balance.

+ Details

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

- Definition

For trading assets which the fair value option has been elected, this item represents the carrying amount of those positions that are 90 days or more past due, in nonaccrual status, or both.

+ Details

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Period Type:	instant

- Definition

The amount of mortgage servicing rights (MSRs) as of the balance sheet date.

+ Details

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

- Definition

Aggregate notional amount of unfunded letters of credit.

+ Details

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

- Definition

Carrying amount of unfunded loan commitments related to certain credit related products selected for fair value accounting.

+ Details

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

- Definition

This item represents the estimated amount of gains or losses included in earnings during the period attributable to changes in instrument-specific credit risk arising from loans and other receivables held as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 19
-Subparagraph c(1)

+ Details

Name:	us-gaap_FairValueOptionCreditRiskGainsLossesOnAssets
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the estimated amount of gains and losses from fair value changes included in earnings that are attributable to changes in the instrument-specific credit risk of liabilities with fair values that have been significantly affected during the reporting period by changes in the instrument-specific credit risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 19
-Subparagraph d(1)

+ Details

Name:	us-gaap_FairValueOptionCreditRiskGainsLossesOnLiabilities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For loans held as assets for which the fair value option has been elected, this item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of those loans that are 90 days or more past due, in nonaccrual status, or both.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph e(3)

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_FairValueOptionQuantitativeDisclosuresLineItems
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FAIR VALUE ELECTIONS (Details 2) (USD $)	3 Months Ended		6 Months Ended					6 Months Ended			6 Months Ended			6 Months Ended	12 Months Ended
FAIR VALUE ELECTIONS (Details 2) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Jun. 30, 2011 Certain credit products (Trading account assets)	Dec. 31, 2010 Certain credit products (Trading account assets)	Jun. 30, 2011 Certain credit products (Loans)	Jun. 30, 2010 Certain credit products (Loans)	Dec. 31, 2010 Certain credit products (Loans)	Jun. 30, 2011 Consolidated VIEs Certain mortgage loans (HFS)	Jun. 30, 2010 Consolidated VIEs Certain mortgage loans (HFS)	Dec. 31, 2010 Consolidated VIEs Certain mortgage loans (HFS)	Jun. 30, 2011 Certain mortgage loans (HFS)	Dec. 31, 2010 Certain mortgage loans (HFS)	Jun. 30, 2011 Corporate loans.	Dec. 31, 2010 Corporate loans.	Jun. 30, 2011 Consumer loans.	Dec. 31, 2010 Consumer loans.	Jun. 30, 2011 Long-term debt	Dec. 31, 2010 Long-term debt	Jun. 30, 2011 Short-term borrowings	Dec. 31, 2010 Short-term borrowings
FAIR VALUE ELECTIONS
Gain (loss) on change in estimated fair value of debt liabilities due to change in company's own credit risk	$ 241,000,000	$ 455,000,000	$ 128,000,000	$ 450,000,000
Notional amount of unfunded letters of credit	600,000,000		600,000,000		1,100,000,000
Fair Value Option Quantitative Disclosures
Carrying amount reported on the Consolidated Balance Sheet						15,049,000,000	14,241,000,000	3,108,000,000		1,748,000,000				4,198,000,000	7,230,000,000	303,000,000	425,000,000	1,395,000,000	1,718,000,000	25,243,000,000	22,055,000,000	1,938,000,000	2,429,000,000
Aggregate unpaid principal balance in excess of fair value						232,000,000	167,000,000	(76,000,000)		(88,000,000)				146,000,000	81,000,000	420,000,000	357,000,000	474,000,000	527,000,000	36,000,000	477,000,000	125,000,000	81,000,000
Balance of non-accrual loans or loans more than 90 days past due						41,000,000	221,000,000								1,000,000	37,000,000	45,000,000	106,000,000	133,000,000
Aggregate unpaid principal balance in excess of fair value						47,000,000	57,000,000				945,000,000		857,000,000		1,000,000	41,000,000	43,000,000	113,000,000	139,000,000
Unfunded loan commitments outstanding, certain credit related products								721,000,000		621,000,000
Changes in fair value due to instrument-specific credit risk gain (loss)								34,000,000	27,000,000		(169,000,000)	(64,000,000)		(200,000)	(1,000,000)
Mortgage servicing rights (MSRs)	$ 4,258,000,000		$ 4,258,000,000		$ 4,554,000,000