Discontinued Operations - Operating Results of the Disposal Group (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment of discontinued operations		$ (9,283)	$ (113,007)
Grass Valley
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment of discontinued operations			(113,000)
Grass Valley \| Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 1,334		109,195
Cost of sales	(1,008)		(70,199)
Gross profit	326		38,996
Selling, general and administrative expenses	(574)		(37,435)
Research and development expenses	(610)		(15,083)
Asset impairment of discontinued operations	0		(113,007)
Interest expense, net	(12)		(432)
Non-operating pension cost	27		(169)
Loss before taxes	$ (843)		$ (127,130)

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 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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