PROPERTY AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 100,719	$ 91,052
Accumulated depreciation and amortization	(43,000)	(44,744)
Property and equipment, net	57,719	46,308
Depreciation expense for property and equipment	12,495	10,053	8,435
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	36,933	28,527
Furniture, Office Equipment and Research Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,395	25,837
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 36,391	$ 36,688