Income Taxes Reconciliation of Unrecognized Tax Benefits (Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Undistributed earnings of its foreign subsidiaries for which the Company has not provided US Deferred income taxes	$ 18,328
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	235
Unrecognized Tax Benefits	1,006	$ 815	$ 983	$ 2,487
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	52	0	168
Unrecognized Tax Benefits, Decrease Resulting from Foreign Currency Translation	43	(131)	(116)
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	111	293	13
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	0	(330)	(1,569)
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	$ (15)	$ 0	$ 0