ALLOWANCE FOR CREDIT LOSSES (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Allowance for credit losses
Allowance for loan losses at the beginning of period	$ 34,362	$ 46,197	$ 40,655	$ 36,033
Gross credit losses	(5,217)	(8,499)	(18,254)	(26,707)
Gross recoveries	703	840	2,324	2,702
Net credit losses (NCLs)	(4,514)	(7,659)	(15,930)	(24,005)
Net reserve builds (releases)	(1,591)	(1,470)	(7,023)	(4,104)
Net specific reserve builds (releases)	126	(523)	222	654
Total provision for credit losses	3,049	5,666	9,129	20,555
Other, net	(845)	(530)	(1,802)	11,091
Allowance for loan losses at the end of period	32,052	43,674	32,052	43,674
Allowance for credit losses on unfunded lending commitments
Allowance for credit losses on unfunded lending commitments at beginning of period	1,097	1,054	1,066	1,157
Provision (release) for unfunded lending commitments	43	26	55	(80)
Allowance for credit losses on unfunded lending commitments at end of period	1,139	1,102	1,139	1,102
Total allowance for loans, leases, and unfunded lending commitments at end of period	$ 33,191	$ 44,776	$ 33,191	$ 44,776

Reflects the amount of loans and leases that have been removed or charged off from both loan receivables and the reserve for credit losses, net of any recoveries of previously removed or charged off credit losses.

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

- Definition

Represents the net amount of other allowances for credit losses related to loan and lease receivables.

+ Details

Name:	c_LoansAndLeasesReceivableAllowanceForCreditLossesOtherNet
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The reserve to cover probable credit losses related to loans and leases receivable and unfunded lending commitments as of the balance sheet date.

+ Details

Name:	c_LoansAndLeasesReceivableAndUnfundedLendingCommitmentsAllowance
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the balance sheet activity during the period for the amount charged against earnings for credit losses on loans and leases receivable that are expected and were collectively evaluated for impairment.

+ Details

Name:	c_LoansAndLeasesReceivableReserveBuildsOrReleasesNet
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reflects the balance sheet activity during the period for the amount charged against earnings for credit losses on loans and leases receivable that are expected and were individually evaluated for impairment.

+ Details

Name:	c_LoansAndLeasesReceivableSpecificReserveBuildsOrReleasesNet
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Reflects the balance sheet side of the amount charged against earnings during the period for credit losses related to unfunded lending commitments.

+ Details

Name:	c_ProvisionForUnfundedLendingCommitments
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The reserve to cover probable credit losses related to unfunded lending commitments as of the balance sheet date.

+ Details

Name:	c_UnfundedLendingCommitmentsAllowanceForCreditLosses
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

Reflects the amount charged against earnings during the period as bad debt expense, net of recoveries of previously expensed credit losses.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

+ Details

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

- Definition

Reflects a reduction in bad debt expense attributable to collections of loans and lease receivables which had previously been fully or partially charged off as bad debts.

+ References

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRecoveriesOfBadDebts
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRollForward
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the amount of loans and leases that have been removed, or charged off, from both loan receivables and the reserve for credit losses, typically because they are considered to be not salvageable or have been purchased by unconsolidated collection entities.

+ References

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The allowance for loan and lease losses represents the reserve to cover probable credit losses related to specifically identified loans and leases, as well as probable credit losses inherent in the remainder of the loan portfolio as of the balance sheet date. For banks, include currently required allocated transfer risk reserves. Include carryover of or adjustments to the allowance for loan losses in connection with business combinations determined to be appropriate.

+ References

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Paragraph 8

-Subparagraph a(ii)

-Subsection I

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 8, 9

+ Details

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