Segment Information - Net Sales Activity by Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2016	Jul. 26, 2015	Jul. 31, 2016	Jul. 26, 2015
Revenue from External Customer [Line Items]
Net sales	$ 135,911	$ 125,712	$ 267,056	$ 255,800
Semiconductor Products Group [Member]
Revenue from External Customer [Line Items]
Net sales	135,911	125,648	267,056	253,895
All others [Member]
Revenue from External Customer [Line Items]
Net sales	$ 0	$ 64	$ 0	$ 1,905

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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