REVENUE - Geographic Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 227,375	$ 205,592	$ 492,966	$ 418,138
Percent of total revenue	100.00%	100.00%	100.00%	100.00%
U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 142,811	$ 119,682	$ 315,228	$ 223,673
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	8,930	8,873	24,272	37,702
United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Revenue	21,259	16,686	43,096	41,235
Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Revenue	34,878	33,395	66,816	67,581
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenue	$ 19,497	$ 26,956	$ 43,554	$ 47,947
Total revenue | U.S.
Disaggregation of Revenue [Line Items]
Percent of total revenue	63.00%	59.00%	63.00%	54.00%
Total revenue | Other Americas
Disaggregation of Revenue [Line Items]
Percent of total revenue	4.00%	4.00%	5.00%	9.00%
Total revenue | United Kingdom (“U.K.”)
Disaggregation of Revenue [Line Items]
Percent of total revenue	9.00%	8.00%	9.00%	10.00%
Total revenue | Europe (excluding U.K.), Middle East, and Africa
Disaggregation of Revenue [Line Items]
Percent of total revenue	15.00%	16.00%	14.00%	16.00%
Total revenue | Asia-Pacific
Disaggregation of Revenue [Line Items]
Percent of total revenue	9.00%	13.00%	9.00%	11.00%