Foreign Operations - Net Sales to External Customers by Geographic Area (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
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 170,303	$ 182,717	$ 162,523	$ 164,698	$ 181,152	$ 175,652	$ 177,580	$ 161,406	$ 680,241	$ 695,790	$ 651,371
United States
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									315,214	345,838	338,338
Asia (excluding the PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									124,657	104,668	89,527
People's Republic of China (PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									91,446	83,036	77,224
Europe
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									85,228	79,183	74,113
Latin America
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									30,954	54,113	47,286
Other
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									$ 32,742	$ 28,952	$ 24,883