PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 181,367	$ 174,849
Accumulated depreciation and amortization	159,464	144,703
Property, plant and equipment, net	21,903	30,146
Capitalized Computer Software, Additions	1,900	1,300	$ 5,100
Capitalized Computer Software, Amortization	2,800	3,000	1,800
Annual depreciation and amortization	$ 13,100	15,200	$ 13,700
Internal Use Software [Domain]
Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Useful Life	3 years
Computer and video equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 127,322	120,853
Manufacturing tooling and testbeds [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	3,591	3,567
Office equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,036	4,958
Furniture, fixtures and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,639	10,691
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 34,779	$ 34,780