SEGMENT AND GEOGRAPHIC INFORMATION (Total Revenue by Major Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total revenues	$ 241,160	$ 226,367	$ 212,673	$ 202,534	$ 219,074	$ 197,523	$ 197,043	$ 183,077	$ 882,734	$ 796,717	$ 696,832
Total long-lived assets	213,147				220,354				213,147	220,354
United States
Segment Reporting Information [Line Items]
Total revenues									680,824	596,303	521,244
Total long-lived assets	192,900				197,897				192,900	197,897
Europe
Segment Reporting Information [Line Items]
Total revenues									103,057	99,207	85,448
Total long-lived assets	19,169				21,218				19,169	21,218
Rest of the World
Segment Reporting Information [Line Items]
Total revenues									98,853	101,207	$ 90,140
Total long-lived assets	$ 1,078				$ 1,239				$ 1,078	$ 1,239