Discontinued Operations - Operating Results of the Disposal Group (Details) - Grass Valley - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 1,000
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	1,334	$ 87,221	$ 109,195	$ 263,434
Cost of sales	(1,008)	(50,622)	(70,199)	(153,012)
Gross profit	326	36,599	38,996	110,422
Selling, general and administrative expenses	(574)	(21,924)	(37,435)	(66,785)
Research and development expenses	(610)	(7,360)	(15,083)	(28,526)
Amortization of intangibles	0	(3,218)	0	(11,695)
Asset impairment of discontinued operations	0	(342,146)	(113,007)	(342,146)
Interest expense, net	(12)	(198)	(432)	(611)
Non-operating pension benefit (cost)	27	(55)	(169)	(166)
Loss before taxes	$ (843)	$ (338,302)	$ (127,130)	$ (339,507)

Disposal Group, Discontinued Operations, Non-operating Pension Cost

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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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