Segment Information Revenues and Operating Net Assets by Geographical Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	$ 817,740	$ 794,020	$ 863,980
Long-lived Assets	703,860	708,160	833,920
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	62,360	65,490	70,760
Long-lived Assets	54,790	45,050	50,930
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	36,630	32,230	30,280
Long-lived Assets	51,120	51,060	49,830
Other Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	15,260	13,620	17,000
Long-lived Assets	7,930	7,800	5,840
Non-US [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	114,250	111,340	118,040
Long-lived Assets	113,840	103,910	106,600
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Sales	703,490	682,680	745,940
Long-lived Assets	$ 590,020	$ 604,250	$ 727,320