SEGMENT AND GEOGRAPHIC INFORMATION - Total Revenue by Major Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 282,164	$ 249,309	$ 540,801	$ 486,079
United States
Segment Reporting Information [Line Items]
Revenues	219,266	191,872	420,363	373,101
Europe
Segment Reporting Information [Line Items]
Revenues	32,499	31,663	61,315	61,098
Rest of World
Segment Reporting Information [Line Items]
Revenues	$ 30,399	$ 25,774	$ 59,123	$ 51,880