Discontinued Operations (Statement of Operations) (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 19, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale, net of income taxes	$ 5,411
High Voltage Product Line | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue		$ 22,620	$ 42,659
Cost of revenue		13,035	19,462
Gross profit		9,585	23,197
Selling, general and administrative		6,886	7,884
Research and development		2,087	2,084
Total operating expenses		8,973	9,968
Income from operations of discontinued operations		612	13,229
Other components of defined benefit plans, net		938	628
Other income and expense, net		(78)	(26)
Gain on sale, net of income taxes		5,411	0
Income tax benefit (provision)		1,011	(3,098)
Income from discontinued operations, net of income taxes		$ 7,894	$ 10,733