Discontinued Operations - Assets and Liabilities of the Disposal Group (Details) - Grass Valley - Discontinued Operations, Held-for-sale $ in Thousands	Dec. 31, 2019 USD ($)
Assets:
Cash and cash equivalents	$ 18,405
Receivables, net	117,386
Inventories, net	55,002
Other current assets	35,187
Property, plant and equipment, less accumulated depreciation	61,233
Operating lease right-of-use assets	16,902
Goodwill	26,707
Intangible assets, less accumulated amortization	143,459
Deferred income taxes	59,560
Other long-lived assets	21,652
Impairment of disposal group	(180,358)
Total assets of discontinued operations	375,135
Liabilities:
Accounts payable	52,425
Accrued liabilities	83,349
Postretirement benefits	6,224
Deferred income taxes	2,740
Long-term operating lease liabilities	20,459
Other long-term liabilities	5,082
Total liabilities of discontinued operations	$ 170,279