This element represents the amount of liquidity agreements for customer TOB trusts.

No definition available.

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

- Definition

Represents the amount of liquidity arrangements for other non-consolidated proprietary trusts.

+ References

No definition available.

+ Details

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

- Definition

The notional amount of reimbursement agreements in place, which offset liquidity agreements for customer TOB trusts.

+ References

No definition available.

+ Details

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

- Definition

Represent the threshold of ownership percentage on Residual value of customers TOBs in which if the customers own less than the threshold will have to reimburse the entity for any payment made under the liquidity arrangement.

+ References

No definition available.

+ Details

Name:	c_TheThresholdOwnershipPercentageOnResidualValueByCustomerTOBInWhichReimbursementAgreementApplied
Namespace Prefix:	c_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719

+ Details

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

- 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.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=c_ClientIntermediationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=c_MunicipalSecuritiesTenderOptionBondTrustsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Municipal Securities Tender Option Bond Trusts (Details) - USD ($) $ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Client intermediation
Variable Interest Entity
Proceeds from new securitizations	$ 0.3	$ 0.2	$ 0.5	$ 0.7
Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Liquidity agreements, customer TOB trust	3.8		3.8		$ 3.2
Notional amount of offsetting reimbursement agreements	1.9		1.9		2.0
Liquidity agreements, other trusts	$ 6.3		$ 6.3		$ 6.1
Municipal securities tender option bond trusts (TOBs) \| Maximum
Variable Interest Entity
The threshold ownership percentage on Residual value of customers TOBs for which the reimbursement agreement applied			25.00%