SEGMENTS - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Adjusted contribution	$ 14,224	$ 10,595
Plus: FI Share and other third-party costs	18,489	16,286
Revenues	32,713	26,881
Cardlytics Direct
Segment Reporting Information [Line Items]
Adjusted contribution	14,222	9,440
Plus: FI Share and other third-party costs	17,899	15,014
Revenues	32,121	24,454
Other Platform Solutions
Segment Reporting Information [Line Items]
Adjusted contribution	2	1,155
Plus: FI Share and other third-party costs	590	1,272
Revenues	$ 592	$ 2,427

Adjusted contribution represents our revenue less FI Share and other third-party costs. We refined our definition of adjusted contribution used by our CODM to exclude the impact of non-cash charges related to the issuance of equity to our FI partners and the impact of amortization and impairment of deferred FI implementation costs.

No definition available.

+ Details

Name:	cdlx_AdjustedContribution
Namespace Prefix:	cdlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Financial Institution Share And Other Third-Party Costs, Excluding Non-cash Equity Expense and Deferred Implementation Costs

+ References

No definition available.

+ Details

Name:	cdlx_FinancialInstitutionShareAndOtherThirdPartyCostsExcludingNoncashEquityExpenseandDeferredImplementationCosts
Namespace Prefix:	cdlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cdlx_CardlyticDirectSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cdlx_OtherPlatformSolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: