SEGMENT INFORMATION - Geographic Information about Revenue and Long-Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenue and long-lived assets by geography
Revenue	$ 1,186,658	$ 1,059,122	$ 2,292,501	$ 2,054,197
Property and equipment, net of accumulated depreciation and amortization	361,550		361,550		$ 318,800
United States
Revenue and long-lived assets by geography
Revenue	774,095	708,571	1,486,476	1,366,151
Property and equipment, net of accumulated depreciation and amortization	334,439		334,439		289,756
All other countries
Revenue and long-lived assets by geography
Revenue	412,563	$ 350,551	806,025	$ 688,046
Property and equipment, net of accumulated depreciation and amortization	$ 27,111		$ 27,111		$ 29,044