SEGMENTS - Revenue by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Adjusted Contribution	$ 82,182	$ 95,219	$ 69,450
Plus: FI Share and other third-party costs	104,710	115,211	81,234
Revenues	186,892	210,430	150,684
Cardlytics Direct
Segment Reporting Information [Line Items]
Adjusted Contribution	82,182	95,219	69,364
Plus: FI Share and other third-party costs	104,710	115,211	79,959
Revenues	186,892	210,430	149,323
Other Platform Solutions
Segment Reporting Information [Line Items]
Adjusted Contribution	0	0	86
Plus: FI Share and other third-party costs	0	0	1,275
Revenues	$ 0	$ 0	$ 1,361