Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			3
Segment Information
Net sales	$ 284,178	$ 262,476	$ 836,964	$ 745,345
Income (Loss) from Operations	60,922	46,696	154,462	114,463
Total Assets	1,094,613	1,068,383	1,094,613	1,068,383	$ 1,037,523
Cash and cash equivalent	166,961	204,171	166,961	204,171	168,514	$ 226,537
Intersegment elimination
Segment Information
Net sales	8,409	4,888	23,536	17,484
Administrative and all other
Segment Information
Income (Loss) from Operations	(667)	0	(3,470)	(3,160)
Total Assets	(223,633)	(114,886)	(223,633)	(114,886)	(150,970)
Cash and cash equivalent	87,500	116,000	87,500	116,000	80,200
North America
Segment Information
Net sales	239,898	213,254	705,932	612,765
Income (Loss) from Operations	56,873	41,775	151,323	110,521
Total Assets	1,080,910	946,180	1,080,910	946,180	953,033
North America | Intersegment elimination
Segment Information
Net sales	683	625	1,889	2,403
Europe
Segment Information
Net sales	42,020	47,137	124,096	126,752
Income (Loss) from Operations	3,584	5,139	4,783	7,443
Total Assets	208,888	211,083	208,888	211,083	208,640
Europe | Intersegment elimination
Segment Information
Net sales	140	175	740	424
Asia/Pacific
Segment Information
Net sales	2,260	2,085	6,936	5,828
Income (Loss) from Operations	1,132	(218)	1,826	(341)
Total Assets	28,448	26,006	28,448	26,006	$ 26,820
Asia/Pacific | Intersegment elimination
Segment Information
Net sales	$ 7,586	$ 4,088	$ 20,907	$ 14,657