Assets Held for Sale - Summary of Major Assets and Liabilities Classified as Held For Sale (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of assets held for sale		$ 0	$ (23,931)	$ 0
Total assets held for sale	$ 23,193	0	23,193
Total liabilities held for sale	1,736	$ 0	1,736
Hirschmann Jv [Member] | Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivables, net	4,551		4,551
Inventories, net	2,848		2,848
Other current assets	1,131		1,131
Property, plant, and equipment, less accumulated depreciation	1,946		1,946
Intangible assets, less accumulated amortization	4,405		4,405
Goodwill	5,477		5,477
Other long-lived assets	26,766		26,766
Total assets of disposal group	47,124		47,124
Impairment of assets held for sale	(23,900)		(23,931)
Total assets held for sale	23,193		23,193
Accrued liabilities	1,288		1,288
Postretirement benefits	448		448
Total liabilities held for sale	$ 1,736		$ 1,736