Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue
Product warranty period		1 year
Change in contract liabilities	$ (400)	$ (400)
Contract liabilities	17,774	17,774		$ 18,145
Deferred revenue	14,393	14,393		16,181
Long-term deferred revenue	3,381	3,381		$ 1,964
ASC 606 Adjustments
Disaggregation of Revenue
Contract liabilities	2,880	2,880
ASC 606 Adjustments | ASU 2014-09
Disaggregation of Revenue
Reclassification gross decrease in customer contract liabilities	1,600	$ 1,600	$ 1,600
ASC 606 Adjustments | Maximum
Disaggregation of Revenue
Unsatisfied extended warranty performance obligations, period		24 months
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
Systems | ASC 606 Adjustments
Disaggregation of Revenue
Increase in revenue	$ (600)	$ 1,300
Aftermarket | Minimum
Disaggregation of Revenue
Extended warranty period		1 year
Aftermarket | Maximum
Disaggregation of Revenue
Extended warranty period		3 years