REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 96,933	$ 87,646
Merchant card fees
Disaggregation of Revenue [Line Items]
Total revenues	89,086	79,594
Outsourced services
Disaggregation of Revenue [Line Items]
Total revenues	5,662	5,977
Other services
Disaggregation of Revenue [Line Items]
Total revenues	1,129	1,433
Equipment
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,056	$ 642