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Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Comprehensive Income (Details 2) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign Currency Translation Adjustments, Beginning balance			$ (4,186)
Foreign Currency Translation Adjustments, Other comprehensive loss before reclassifications			(796)
Foreign Currency Translation Adjustments, Amounts reclassified from accumulated other comprehensive loss			0
Foreign Currency Translation Adjustments, Net current period other comprehensive (loss) income			(796)
Foreign Currency Translation Adjustments, Ending balance	$ (4,982)		(4,982)
Defined Benefit Pension Items, Beginning balance			(13,673)
Defined Benefit Pension Items, Other comprehensive loss before reclassifications			0
Defined Benefit Pension Items, Amounts reclassified from accumulated other comprehensive loss	118	$ 88	236	$ 161
Defined Benefit Pension Items, Net current period other comprehensive (loss) income			236
Defined Benefit Pension Items, Ending balance	(13,437)		(13,437)
Beginning balance			(17,859)
Other comprehensive loss before reclassifications			(796)
Amounts reclassified from accumulated other comprehensive loss			236
Net current period other comprehensive (loss) income			(560)
Ending balance	$ (18,419)		$ (18,419)