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

Reconciliation of Unrecognized Tax Benefits, Including Amounts Pertaining to Examined Tax Returns [Roll Forward]

No definition available.

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

This element represents the amount of statutory penalties accrued under foreign tax laws as of the date of the statement of financial position for a tax position claimed or expected to be claimed by the entity, in tax return, that does not meet minimum statutory threshold to avoid payment of penalties.

No definition available.

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

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties, net of resulting tax.

No definition available.

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

This element represents the total of interest expense recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties, net of related tax.

No definition available.

Name:	c_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpenseNetOfTax
Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 217
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-217

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-15

Name:	us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.