REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 177,176	$ 154,187
Platform Solutions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	161,619	140,617
Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 15,557	$ 13,570