Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Taxes [Abstract]
Unrecognized tax benefits	$ 3,300			$ 3,300
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	$ 300			$ 300
Effective tax rate	26.20%		68.40%	24.90%	57.90%
Deferred income taxes	$ 7,990	$ 7,360		$ 7,990
Taxes on foreign earnings repatriated			$ 2,500
Reversal of taxes on foreign earnings repatriated due to 2017 Tax Act		$ (1,600)
Unremitted earnings of foreign subsidiaries	8,100			8,100
Unrecognized deferred tax liability on unremitted earnings of foreign subsidiaries	400			400
Internal Revenue Service (IRS) | Tax Years 2011, 2012 and 2013
Income Taxes [Abstract]
Disallowed research tax credits being litigated	$ 2,500			2,500
Internal Revenue Service (IRS) | Tax Years 2011 to Date
Income Taxes [Abstract]
Income Tax Credits and Adjustments				$ 9,600