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Cash and Investments - Cash, Cash Equivalents and Available-for-Sale Investments (Details) - USD ($) $ in Thousands | Sep. 28, 2019 | Dec. 29, 2018
--- | --- | ---
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | $ 144,059 | $ 151,878
Gross Unrealized Gains | 52 | 0
Gross Unrealized Losses | (1) | (86)
Estimated Fair Market Value | 144,110 | 151,792
Cash [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 34,862 | 108,845
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Market Value | 34,862 | 108,845
Money market funds [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 9,162 | 113
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Market Value | 9,162 | 113
Commercial paper [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 5,985 | 1,993
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Market Value | 5,985 | 1,993
Certificates of deposits [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 1,000 | 0
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Market Value | 1,000 | 0
Certificates of deposits [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 29,003 | 9,500
Gross Unrealized Gains | 4 | 0
Gross Unrealized Losses | 0 | (3)
Estimated Fair Market Value | 29,007 | 9,497
Commercial paper [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 16,760 | 7,933
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (1) | (1)
Estimated Fair Market Value | 16,759 | 7,932
Corporate debt securities [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 36,894 | 15,788
Gross Unrealized Gains | 33 | 0
Gross Unrealized Losses | 0 | (58)
Estimated Fair Market Value | 36,927 | 15,730
Asset-backed Securities [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Amortized Cost | 10,393 | 7,706
Gross Unrealized Gains | 15 | 0
Gross Unrealized Losses | 0 | (24)
Estimated Fair Market Value | $ 10,408 | $ 7,682

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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