Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 60,679	$ 54,362
Concentration Risk, Percentage	17.20%	0.60%
Process Control Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	$ 43,876	$ 36,459
Lithography Revenue [Domain]
Segment Reporting Information [Line Items]
Revenues	17	170
Software [Domain]
Segment Reporting Information [Line Items]
Revenues	7,498	7,422
Sales Revenue, Goods, Net [Member]
Segment Reporting Information [Line Items]
Revenues	6,330	7,160
Sales Revenue, Services, Net [Member]
Segment Reporting Information [Line Items]
Revenues	2,958	3,151
Sales Revenue, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	$ 60,679	$ 54,362
Sales [Member] | Percentage of Process Control Revenue [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	72.00%	67.00%
Sales [Member] | Percentage of Lithography Revenue [Member] [Domain]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	0.00%	0.00%
Sales [Member] | Percentage of Software Revenue [Domain]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	13.00%	14.00%
Sales [Member] | Percentage of Parts [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	10.00%	13.00%
Sales [Member] | Percentage of Service [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	5.00%	6.00%
Sales [Member] | Percentage of Total Revenue [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	100.00%	100.00%
UNITED STATES
Segment Reporting Information [Line Items]
Revenues	$ 9,009	$ 7,388
TAIWAN, PROVINCE OF CHINA
Segment Reporting Information [Line Items]
Revenues	13,833	22,035
JAPAN
Segment Reporting Information [Line Items]
Revenues	3,208	2,937
CHINA
Segment Reporting Information [Line Items]
Revenues	14,101	8,825
South Korea [Domain]
Segment Reporting Information [Line Items]
Revenues	9,530	1,623
SINGAPORE
Segment Reporting Information [Line Items]
Revenues	3,266	7,047
Asia [Member]
Segment Reporting Information [Line Items]
Revenues	114	871
GERMANY
Segment Reporting Information [Line Items]
Revenues	3,080	697
Other Europe [Domain]
Segment Reporting Information [Line Items]
Revenues	4,538	2,939
Sales [Member]
Segment Reporting Information [Line Items]
Revenues	$ 60,679	$ 54,362