Segment Reporting and Geographic Information - Schedule of Revenue from External Customers by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 60,892	$ 73,096
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	$ 39,158	$ 48,033
Process Control [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	64.00%	66.00%
Lithography [Member]
Segment Reporting Information [Line Items]
Revenues	$ 3,614	$ 8,069
Lithography [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	6.00%	11.00%
Software Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 7,037	$ 7,455
Software Revenue [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	12.00%	10.00%
Parts Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 8,077	$ 6,985
Parts Revenue [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	13.00%	10.00%
Service Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 3,006	$ 2,554
Service Revenue [Member] | Sales [Member] | Product [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	5.00%	3.00%