Operating Segments and Geographic Information (Operations by Geographic Area) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 209,008	$ 206,783	$ 201,424	$ 203,828	$ 173,000	$ 165,259	$ 157,489	$ 160,566	$ 821,043	$ 656,314	$ 641,443
Long-Lived Assets	576,996				522,894				576,996	522,894	429,133
United States
Segment Reporting Information [Line Items]
Net sales									225,621	158,136	164,478
Long-Lived Assets	370,964				326,199				370,964	326,199	218,439
China
Segment Reporting Information [Line Items]
Net sales									272,184	236,961	227,993
Long-Lived Assets	57,404				62,728				57,404	62,728	65,994
Germany
Segment Reporting Information [Line Items]
Net sales									89,203	79,480	76,569
Long-Lived Assets	114,497				101,725				114,497	101,725	110,240
Other
Segment Reporting Information [Line Items]
Net sales									234,035	181,737	172,403
Long-Lived Assets	$ 34,131				$ 32,242				$ 34,131	$ 32,242	$ 34,460