Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 67,418	$ 62,701	$ 128,097	$ 117,063
Concentration Risk, Percentage			11.20%	1.60%
Process Control Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	47,711	34,464	$ 91,586	$ 70,922
Lithography Revenue [Domain]
Segment Reporting Information [Line Items]
Revenues	3,533	11,480	3,550	11,650
Software [Domain]
Segment Reporting Information [Line Items]
Revenues	6,895	7,780	14,394	15,202
Sales Revenue, Goods, Net [Member]
Segment Reporting Information [Line Items]
Revenues	7,348	5,993	13,678	13,153
Sales Revenue, Services, Net [Member]
Segment Reporting Information [Line Items]
Revenues	1,931	2,984	4,889	6,136
Sales Revenue, Segment [Member]
Segment Reporting Information [Line Items]
Revenues	$ 67,418	$ 62,701	$ 128,097	$ 117,063
Sales [Member] | Percentage of Process Control Revenue [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	71.00%	55.00%	72.00%	61.00%
Sales [Member] | Percentage of Lithography Revenue [Member] [Domain]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	5.00%	18.00%	2.00%	10.00%
Sales [Member] | Percentage of Software Revenue [Domain]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	10.00%	12.00%	11.00%	13.00%
Sales [Member] | Percentage of Parts [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	11.00%	10.00%	11.00%	11.00%
Sales [Member] | Percentage of Service [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	3.00%	5.00%	4.00%	5.00%
Sales [Member] | Percentage of Total Revenue [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%	100.00%
UNITED STATES
Segment Reporting Information [Line Items]
Revenues	$ 9,182	$ 5,646	$ 18,190	$ 13,034
TAIWAN, PROVINCE OF CHINA
Segment Reporting Information [Line Items]
Revenues	20,323	14,535	34,156	36,570
JAPAN
Segment Reporting Information [Line Items]
Revenues	3,468	3,164	6,677	6,101
CHINA
Segment Reporting Information [Line Items]
Revenues	5,904	10,824	20,005	19,649
SINGAPORE
Segment Reporting Information [Line Items]
Revenues	1,945	14,879	5,211	21,926
Asia [Member]
Segment Reporting Information [Line Items]
Revenues	1,444	1,674	1,559	2,545
GERMANY
Segment Reporting Information [Line Items]
Revenues	4,789	4,235	7,869	4,932
Sales [Member]
Segment Reporting Information [Line Items]
Revenues	$ 67,418	$ 62,701	$ 128,097	$ 117,063