Discontinued Operations - Assets and Liabilities of the Disposal Group (Details) - Grass Valley - Discontinued Operations, Held-for-sale [Member] - USD ($) $ in Thousands	Jun. 28, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 33,337	$ 18,405
Receivables, net	90,492	117,386
Inventories, net	49,997	55,002
Other current assets	38,626	35,187
Plant, property, and equipment, less accumulated depreciation	65,056	61,233
Operating lease right-of-use assets	15,631	16,902
Goodwill	26,067	26,707
Intangible assets, less accumulated depreciation	150,214	143,459
Deferred income taxes	58,148	59,560
Other long-lived assets	12,201	21,652
Impairment of disposal group	(289,447)	(180,358)
Total Assets of discontinued operations	250,322	375,135
Liabilities
Accounts payable	42,482	52,425
Accrued liabilities	38,816	83,349
Postretirement benefits	4,976	6,224
Deferred income taxes	2,404	2,740
Long-term operating lease liabilities	18,745	20,459
Other long-term liabilities	2,250	5,082
Total Liabilities of discontinued operations	$ 109,673	$ 170,279