Discontinued Operations - Operating Results of the Disposal Group (Details) - USD ($) $ in Thousands	3 Months Ended
Apr. 04, 2021	Mar. 29, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment of discontinued operations	$ (6,995)	$ (23,197)
Grass Valley
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment of discontinued operations		(23,200)
Grass Valley \| Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues		51,049
Cost of sales		(35,202)
Gross profit		15,847
Selling, general and administrative expenses		(17,519)
Research and development expenses		(8,499)
Asset impairment of discontinued operations		(23,197)
Interest expense, net		(206)
Non-operating pension cost		(85)
Loss before taxes		$ (33,659)

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 general and administrative expense attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of gross profit 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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Amount of revenue 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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