Discontinued Operations - Assets and Liabilities of the Disposal Group (Details) - Grass Valley - Discontinued Operations, Held-for-sale - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 18,405	$ 13,156
Receivables, net	117,386	129,983
Disposal Group, Including Discontinued Operation, Inventory	55,002	51,416
Other current assets	35,187	25,167
Property, plant and equipment, less accumulated depreciation	61,233	55,010
Operating lease right-of-use assets	16,902
Goodwill	26,707	350,777
Intangible assets, less accumulated amortization	143,459	151,162
Deferred income taxes	57,469	29,559
Other long-lived assets	21,652	16,613
Impairment of disposal group	(180,358)	0
Total Assets of discontinued operations	373,044	822,843
Liabilities:
Accounts payable	52,425	55,148
Accrued liabilities	83,349	91,880
Postretirement benefits	6,224	5,043
Deferred income taxes	2,740	3,834
Long-term operating lease liabilities	20,459
Other long-term liabilities	5,082	8,737
Total liabilities of discontinued operations	$ 170,279	$ 164,642