Discontinued Operations - Operating Results of the Disposal Group (Details) - Grass Valley - Discontinued Operations, Held-for-sale [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 29, 2020	Mar. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 51,049	$ 87,035
Cost of sales	(35,202)	(49,163)
Gross profit	15,847	37,872
Selling, general and administrative expenses	(17,519)	(24,831)
Research and development expenses	(8,499)	(10,907)
Amortization of intangibles	0	(5,178)
Asset impairment of discontinued operations	(23,197)	0
Interest expense, net	(206)	(206)
Non-operating pension income (cost)	(85)	(56)
Loss before taxes	$ (33,659)	$ (3,306)

Disposal Group, Discontinued Operations, Non-operating Pension Cost

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Disposal Group, Including Discontinued Operation, Research and Development Expense

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Amount of costs of goods sold attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of interest expense attributable to disposal group, including, but not limited to, discontinued operation.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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