Investments Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Jul. 04, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and available-for-sale investments, estimated fair value	$ 228,479	$ 228,198
Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and available-for-sale investments, estimated fair value	18,792	26,456
Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and available-for-sale investments, estimated fair value	$ 209,687	$ 201,742

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant