ACQUISITIONS - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		6 Months Ended
	Mar. 10, 2021	Jan. 03, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Contingent consideration related to acquisition			$ 21,239		$ 21,239		$ 0
Consolidated net revenue			142,528	$ 131,816	302,934	$ 299,086
Operating expense			54,038	(54,351)	(13,795)	(116,100)
Cumulative translation adjustment, net of tax, period increase (decrease)			5,000
Goodwill			177,286		177,286		136,091
Canada POS Lending
Business Acquisition [Line Items]
Consolidated net revenue			4,032	$ 0	4,796	0
Goodwill			40,506		40,506		$ 0
Flexiti
Business Acquisition [Line Items]
Equity interests acquired	100.00%
Payments to acquire businesses, gross	$ 86,500
Debt costs in conjunction with the acquisition	6,300
Contingent consideration related to acquisition	20,600
Consolidated net revenue			4,000
Operating expense			13,500
Goodwill	44,901		39,921		39,921
Business combination, consideration transferred, equity interests issued and issuable	8,100
Business combination, consideration transferred, equity interests issued relates to RSU contingent consideration	$ 4,000
Business acquisition, service period term	2 years
Business acquisition, incurred costs related to this acquisition			$ 3,400		3,400
Payments to acquire businesses, net of cash acquired					91,203	0
Flexiti | Minimum
Business Acquisition [Line Items]
Contingent consideration related to acquisition	$ 0
Flexiti | Maximum
Business Acquisition [Line Items]
Contingent consideration related to acquisition	$ 32,800
Ad Astra
Business Acquisition [Line Items]
Equity interests acquired		100.00%
Operating expense					2,600
Goodwill		$ 14,791
Payments to acquire businesses, net of cash acquired		14,400			$ 0	$ 14,418
Insurance amount deductible		$ 15,400