Schedule of Geographic Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 29, 2019	Mar. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 157,186	$ 146,965
United States
Segment Reporting Information [Line Items]
Revenue	64,760	58,113
Germany
Segment Reporting Information [Line Items]
Revenue	23,477	20,069
Rest of Europe
Segment Reporting Information [Line Items]
Revenue	30,770	27,060
China
Segment Reporting Information [Line Items]
Revenue	15,108	15,603
Rest of Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	20,447	24,720
Other Countries
Segment Reporting Information [Line Items]
Revenue	$ 2,624	$ 1,400

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration