Segment Reporting and Geographic Information - Schedule of Revenue from External Customers by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 73,096	$ 60,679
Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	100.00%	100.00%
Process Control [Member]
Segment Reporting Information [Line Items]
Revenues	$ 48,033	$ 43,876
Process Control [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	66.00%	72.00%
Lithography [Member]
Segment Reporting Information [Line Items]
Revenues	$ 8,069	$ 17
Lithography [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	11.00%
Software Revenue
Segment Reporting Information [Line Items]
Revenues	$ 7,455	$ 7,498
Software Revenue | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%	13.00%
Parts [Member]
Segment Reporting Information [Line Items]
Revenues	$ 6,985	$ 6,330
Parts [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%	10.00%
Services [Member]
Segment Reporting Information [Line Items]
Revenues	$ 2,554	$ 2,958
Services [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	3.00%	5.00%