SEGMENTS - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Adjusted contribution	$ 29,630	$ 12,402	$ 53,971	$ 32,781
Plus: FI Share and other third-party costs	29,223	15,820	58,112	40,950
Revenues	58,853	28,222	112,083	73,731
Cardlytics Direct
Segment Reporting Information [Line Items]
Adjusted contribution	27,603	12,402	51,944	32,781
Plus: FI Share and other third-party costs	29,160	15,820	58,049	40,950
Revenues	56,763	28,222	109,993	73,731
Bridg, Inc., Mr. T Merger Sub, Inc. And Shareholder Representative Services LLC Merger Agreement
Segment Reporting Information [Line Items]
Adjusted contribution	2,027	0	2,027	0
Plus: FI Share and other third-party costs	63	0	63	0
Revenues	$ 2,090	$ 0	$ 2,090	$ 0