Business Segment and Foreign Operations - Net Sales to External Customers by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 162,523	$ 177,580	$ 327,221	$ 338,986
United States
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	79,294	85,569	159,045	167,497
Asia (excluding the PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	27,467	26,916	54,867	51,566
People's Republic of China (PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	20,627	21,835	40,744	37,578
Europe
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	20,330	19,740	39,460	37,164
Latin America
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	6,636	15,381	16,666	31,026
Other
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 8,169	$ 8,139	$ 16,439	$ 14,155