Business Segment and Foreign Operations - Net Sales to External Customers 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
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 181,152	$ 175,652	$ 177,580	$ 161,406	$ 160,542	$ 169,185	$ 170,986	$ 150,658	$ 695,790	$ 651,371	$ 602,833
United States
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									345,838	338,338	287,678
Asia (excluding the PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									104,668	89,527	109,960
People's Republic of China (PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									83,036	77,224	74,475
Europe
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									79,183	74,113	65,579
Latin America
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									54,113	47,286	38,985
Other
Schedule of Revenues from Geographical Segments [Line Items]
Net sales									$ 28,952	$ 24,883	$ 26,156