Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 43,215	$ 41,861
Point in time
Disaggregation of Revenue [Line Items]
Total revenue	36,930	40,607
Over time
Disaggregation of Revenue [Line Items]
Total revenue	6,285	1,254
North America
Disaggregation of Revenue [Line Items]
Total revenue	21,046	15,770
China
Disaggregation of Revenue [Line Items]
Total revenue	12,042	13,653
Rest of World
Disaggregation of Revenue [Line Items]
Total revenue	10,127	12,438
Industrial
Disaggregation of Revenue [Line Items]
Total revenue	15,990	18,124
Microfabrication
Disaggregation of Revenue [Line Items]
Total revenue	10,419	14,533
Aerospace and Defense
Disaggregation of Revenue [Line Items]
Total revenue	$ 16,806	$ 9,204