Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 79,380	$ 80,870
Accumulated depreciation and amortization	(54,435)	(65,189)
Property and equipment, net	24,945	15,681
Depreciation and amortization	9,187	10,178	$ 8,319
Test equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,148	39,952
Computer equipment and purchased software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,697	32,175
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,976	2,714
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,559	$ 6,029

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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