Summary of Long-lived Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Long-Lived Assets by Geographical Areas [Line Items]
Property, plant and equipment, net	$ 65,464	$ 61,718
United States
Long-Lived Assets by Geographical Areas [Line Items]
Property, plant and equipment, net	32,029	29,920
Europe
Long-Lived Assets by Geographical Areas [Line Items]
Property, plant and equipment, net	31,696	30,621
China
Long-Lived Assets by Geographical Areas [Line Items]
Property, plant and equipment, net	1,636	1,127
Rest of Asia-Pacific
Long-Lived Assets by Geographical Areas [Line Items]
Property, plant and equipment, net	$ 103	$ 50