REVENUE - Geographic Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 225,951	$ 216,703	$ 718,917	$ 634,841
Percent of total revenue	100.00%	100.00%	100.00%	100.00%
U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 120,971	$ 123,447	$ 436,199	$ 347,120
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	10,737	11,748	35,009	49,450
United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Revenue	25,150	23,034	68,246	64,269
Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Revenue	39,656	34,761	106,472	102,342
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	$ 29,437	$ 23,713	$ 72,991	$ 71,660
Total revenue | U.S.
Disaggregation of Revenue [Line Items]
Percent of total revenue	53.00%	57.00%	61.00%	55.00%
Total revenue | Other Americas
Disaggregation of Revenue [Line Items]
Percent of total revenue	5.00%	5.00%	5.00%	8.00%
Total revenue | United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Percent of total revenue	11.00%	11.00%	9.00%	10.00%
Total revenue | Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Percent of total revenue	18.00%	16.00%	15.00%	16.00%
Total revenue | Asia-Pacific
Disaggregation of Revenue [Line Items]
Percent of total revenue	13.00%	11.00%	10.00%	11.00%