Schedule of Geographic Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$ 384,758	$ 373,598	$ 364,706
Percentage of Total	100.00%	100.00%	100.00%
UNITED STATES
Segment Reporting Information [Line Items]
Revenue	$ 154,756	$ 154,825	$ 140,973
Percentage of Total	40.20%	41.40%	38.70%
GERMANY
Segment Reporting Information [Line Items]
Revenue	$ 55,940	$ 54,743	$ 59,029
Percentage of Total	14.50%	14.70%	16.20%
Rest Of Europe
Segment Reporting Information [Line Items]
Revenue	$ 51,705	$ 48,277	$ 54,308
Percentage of Total	13.40%	12.90%	14.90%
CHINA
Segment Reporting Information [Line Items]
Revenue	$ 44,225	$ 38,491	$ 40,792
Percentage of Total	11.50%	10.30%	11.20%
Rest of Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	$ 60,104	$ 62,467	$ 58,830
Percentage of Total	15.60%	16.70%	16.10%
Other Countries
Segment Reporting Information [Line Items]
Revenue	$ 18,028	$ 14,795	$ 10,774
Percentage of Total	4.80%	4.00%	2.90%