Segment Information Revenues and Operating Net Assets by Geographical Areas (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 211,350	$ 223,780	$ 224,910	$ 217,100	$ 195,210	$ 209,330	$ 213,370	$ 199,830	$ 877,140	$ 817,740	$ 794,020
Long-lived Assets	678,980				703,860				678,980	703,860	708,160
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									62,420	62,360	65,490
Long-lived Assets	54,340				54,790				54,340	54,790	45,050
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									45,040	36,630	32,230
Long-lived Assets	45,160				51,120				45,160	51,120	51,060
Other Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									14,670	15,260	13,620
Long-lived Assets	7,830				7,930				7,830	7,930	7,800
Non-US [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									122,130	114,250	111,340
Long-lived Assets	107,330				113,840				107,330	113,840	103,910
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales									755,010	703,490	682,680
Long-lived Assets	$ 571,650				$ 590,020				$ 571,650	$ 590,020	$ 604,250