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Segment Information (Details) $ in Thousands	3 Months Ended
Segment Information (Details) $ in Thousands	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	3
Segment Information
Net sales	$ 259,244	$ 244,779
Income (Loss) from Operations	30,023	32,684
Total Assets	1,030,352	1,040,342	$ 1,021,663
Cash and cash equivalent	113,407	137,413	160,180	$ 168,514
Intersegment elimination
Segment Information
Net sales	7,195	7,501
Administrative and all other
Segment Information
Income (Loss) from Operations	(1,865)	(1,191)
Total Assets	(320,181)	(183,527)	(280,430)
Cash and cash equivalent	74,400	53,400	113,600
North America
Segment Information
Net sales	221,431	206,212
Income (Loss) from Operations	32,814	36,455
Total Assets	1,155,633	982,149	1,119,012
North America \| Intersegment elimination
Segment Information
Net sales	341	628
Europe
Segment Information
Net sales	35,780	36,293
Income (Loss) from Operations	(384)	(1,589)
Total Assets	167,769	213,259	157,437
Europe \| Intersegment elimination
Segment Information
Net sales	458	349
Asia/Pacific
Segment Information
Net sales	2,033	2,274
Income (Loss) from Operations	(542)	(991)
Total Assets	27,131	28,461	$ 25,644
Asia/Pacific \| Intersegment elimination
Segment Information
Net sales	$ 6,396	$ 6,524