Discontinued Operations (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 19, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of income taxes	$ 0		$ 1,309
Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of shares sold				100.00%
Purchase price				$ 55,055
Net cash proceeds received				47,814
Amounts held in escrow				859
Transaction expenses				$ 2,099
Gain on sale, net of income taxes		$ 5,400
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]
Income from discontinued operations, net of income taxes			$ 1,309
Milestone payments, 2019 and 2020	7,500
Milestone payments due	15,000
Additional payments due	$ 5,000