PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 144,537	$ 122,697
Accumulated depreciation and amortization	(56,226)	(48,944)
Property and equipment, net	88,311	73,753
Depreciation expense for property and equipment	19,967	15,111	$ 12,495
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	49,752	42,026
Furniture, Office Equipment and Research Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	38,129	31,016
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 56,656	$ 49,655