GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill
Balance of goodwill at beginning of period	$ 25,009us-gaap_Goodwill	$ 25,673us-gaap_Goodwill
Foreign exchange translation	(1,214)us-gaap_GoodwillTranslationAdjustments	(577)us-gaap_GoodwillTranslationAdjustments
Smaller acquisitions/divestitures, purchase accounting adjustments and other	(203)	(25)
Sale of Brazil Credicard		(62)
Balance of goodwill at end of period	$ 23,592us-gaap_Goodwill	$ 25,009us-gaap_Goodwill

This element represents the net changes to the recorded value of goodwill due to acquisitions or divestitures, purchase accounting adjustments and other adjustments needed to revise the carrying amount of goodwill.

No definition available.

+ Details

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

- Definition

Write-off of the carrying amount of goodwill associated with discontinued operations in the period.

+ References

No definition available.

+ Details

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

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillTranslationAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration