Business Segment and Foreign Operations - Net Sales to External Customers by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 164,698	$ 161,406
United States
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	79,751	81,928
Asia (excluding the PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	27,400	24,650
People's Republic of China (PRC)
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	20,117	15,743
Europe
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	19,130	17,424
Latin America
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	10,030	15,645
Other
Schedule of Revenues from Geographical Segments [Line Items]
Net sales	$ 8,270	$ 6,016