GOODWILL AND ACQUIRED INTANGIBLES - Other Intangible Assets Subject to Amortization (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Finite-Lived Intangible Assets [Line Items]
Net	$ 136,689
Trade name
Finite-Lived Intangible Assets [Line Items]
Cost	2,700
Accumulated Amortization	(284)
Net	$ 2,416
Weighted Average Remaining Useful Life	2 years 7 months 6 days
Developed technology
Finite-Lived Intangible Assets [Line Items]
Cost	$ 89,500
Accumulated Amortization	(3,349)
Net	$ 86,151
Weighted Average Remaining Useful Life	5 years 9 months 18 days
Merchant relationships
Finite-Lived Intangible Assets [Line Items]
Cost	$ 32,000
Accumulated Amortization	(1,692)
Net	$ 30,308
Weighted Average Remaining Useful Life	4 years 8 months 12 days
Partner relationships
Finite-Lived Intangible Assets [Line Items]
Cost	$ 2,000
Accumulated Amortization	(92)
Net	$ 1,908
Weighted Average Remaining Useful Life	6 years 8 months 12 days
Card-linked subscriber user base
Finite-Lived Intangible Assets [Line Items]
Cost	$ 17,000
Accumulated Amortization	(1,094)
Net	$ 15,906
Weighted Average Remaining Useful Life	4 years 8 months 12 days