PROPERTY AND EQUIPMENT - NET (Property, Plant 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	$ 120,217	$ 100,275
Less accumulated depreciation and amortization	(46,601)	(39,776)
Total	73,616	60,499
Depreciation and amortization expenses	$ 15,217	11,979	$ 12,134
Computer hardware
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	3 years
Property and equipment, gross	$ 49,599	36,612
Building
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	49 years
Property and equipment, gross	$ 34,012	34,002
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	7 years
Property and equipment, gross	$ 13,178	8,990
Office equipment
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	7 years
Property and equipment, gross	$ 9,416	8,307
Leasehold improvements
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	4 years
Property and equipment, gross	$ 7,944	6,801
Purchased computer software
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	5 years
Property and equipment, gross	$ 4,601	4,099
Land improvements
Property, Plant and Equipment [Line Items]
Weighted Average Useful Life (in years)	20 years
Property and equipment, gross	$ 1,467	$ 1,464