SEGMENT AND GEOGRAPHIC INFORMATION - Total Revenue by Major Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 278,834	$ 250,332	$ 819,634	$ 736,411
United States
Segment Reporting Information [Line Items]
Revenues	213,685	194,346	634,047	567,103
Europe
Segment Reporting Information [Line Items]
Revenues	32,609	28,553	93,924	89,623
Rest of World
Segment Reporting Information [Line Items]
Revenues	$ 32,540	$ 27,433	$ 91,663	$ 79,685