GOODWILL AND INTANGIBLE ASSETS - Changes in Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Finite and Indefinite-lived Intangible Assets
Beginning balance	$ 3,525
Acquisitions/renewals/ divestitures	82
Amortization	(69)
Impairments	0
FX translation and other	1
Ending balance	3,539
Mortgage servicing rights (MSRs)	766	$ 759
Total intangible assets	4,305	$ 4,284
Indefinite-lived intangible assets
Finite and Indefinite-lived Intangible Assets
Beginning balance	227
Acquisitions/renewals/ divestitures	0
Amortization	0
Impairments	0
FX translation and other	1
Ending balance	228
Purchased credit card relationships
Finite and Indefinite-lived Intangible Assets
Beginning balance	676
Acquisitions/renewals/ divestitures	0
Amortization	(30)
Impairments	0
FX translation and other	0
Ending balance	646
Credit card contract related intangibles
Finite and Indefinite-lived Intangible Assets
Beginning balance	2,592
Acquisitions/renewals/ divestitures	82
Amortization	(34)
Impairments	0
FX translation and other	0
Ending balance	2,640
Other customer relationships
Finite and Indefinite-lived Intangible Assets
Beginning balance	30
Acquisitions/renewals/ divestitures	0
Amortization	(5)
Impairments	0
FX translation and other	0
Ending balance	25
Present value of future profits
Finite and Indefinite-lived Intangible Assets
Beginning balance	0
Acquisitions/renewals/ divestitures	0
Amortization	0
Impairments	0
FX translation and other	0
Ending balance	$ 0

No definition available.

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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill and excluding mortgage servicing rights, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

No definition available.

+ Details

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

- Definition

Intangible Assets, Excluding Mortgage Servicing Rights Acquisitions (Divestitures)

+ References

No definition available.

+ Details

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

- Definition

This element represents the aggregate amount of amortization of intangible assets excluding mortgage servicing rights (MSRs) during the period.

+ References

No definition available.

+ Details

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

- Definition

This element represents the aggregate amount of impairment of intangible assets excluding mortgage servicing rights (MSRs) during the period.

+ References

No definition available.

+ Details

Name:	c_IntangibleAssetsExcludingMortgageServicingRightsImpairments
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Balance Type:	debit
Period Type:	duration

- Definition

This element represents net changes to the recorded value of intangible assets excluding mortgage servicing rights (MSRs), due to foreign currency translation adjustments and purchase accounting adjustments.

+ References

No definition available.

+ Details

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

- Definition

This element represents the sum of the carrying amounts of all intangible assets excluding goodwill but including mortgage servicing rights, as of the balance sheet date that is net of accumulated amortization and impairment charges.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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