Schedule of Geographic Sales (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 31, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales	$ 94,012	$ 94,656	$ 96,905	$ 79,133	$ 82,212	$ 79,858	$ 79,769	$ 75,071	$ 364,706	$ 316,910	$ 243,796
Percentage of Total									100.00%	100.00%	100.00%
UNITED STATES
Segment Reporting Information [Line Items]
Sales									140,973	107,892	76,437
Percentage of Total									38.70%	34.00%	31.40%
GERMANY
Segment Reporting Information [Line Items]
Sales									59,029	56,287	32,822
Percentage of Total									16.20%	17.80%	13.50%
Rest Of Europe
Segment Reporting Information [Line Items]
Sales									54,308	45,698	41,466
Percentage of Total									14.90%	14.40%	17.00%
CHINA
Segment Reporting Information [Line Items]
Sales									40,792	37,651	21,001
Percentage of Total									11.20%	11.90%	8.60%
Rest of Asia-Pacific
Segment Reporting Information [Line Items]
Sales									58,830	57,802	65,262
Percentage of Total									16.10%	18.20%	26.80%
Other Countries
Segment Reporting Information [Line Items]
Sales									$ 10,774	$ 11,580	$ 6,808
Percentage of Total									2.90%	3.70%	2.70%