PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 705,987	$ 535,132
Less: accumulated depreciation	(358,970)	(260,346)
Property and equipment, net	347,017	274,786
Depreciation	140,059	101,517	$ 78,241
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 522,675	396,961
Computer equipment and software | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	2 years
Computer equipment and software | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 143,191	109,724
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	2 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	11 years
Office equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 34,176	28,447
Office equipment, furniture and fixtures | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	2 years
Office equipment, furniture and fixtures | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives (years)	10 years
Building construction-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,945	$ 0