Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Contract liabilities	$ 35,518	$ 22,142	$ 23,058	$ 30,417	$ 34,106	$ 29,251
Deferred revenue	34,112		21,221
Long-term deferred revenue	$ 1,406		$ 1,837
Systems
Disaggregation of Revenue
Payment upon shipment of tool, as a percent	90.00%
Payment upon installation, as a percent	10.00%
Systems | Minimum
Disaggregation of Revenue
Payment upon delivery of parts, period	30 days
Systems | Maximum
Disaggregation of Revenue
Payment upon delivery of parts, period	60 days