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Amortized Cost and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands | Jun. 27, 2020 | Dec. 28, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 117,666 | $ 116,181
Gross Unrealized Gains | 3,402 | 1,477
Gross Unrealized Losses | 400 | 50
Fair Value | 120,668 | 117,608
Money market investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 14,038 | 15,691
Fair Value | 14,038 | 15,691
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 569 | 572
Gross Unrealized Losses | 84 | 1
Fair Value | 485 | 571
Corporate bonds and direct obligations of government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 100,722 | 97,583
Gross Unrealized Gains | 3,261 | 1,465
Gross Unrealized Losses | 316 | 44
Fair Value | 103,667 | 99,004
U.S. Treasury obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,337 | 2,335
Gross Unrealized Gains | 141 | 12
Gross Unrealized Losses |  | 5
Fair Value | $ 2,478 | $ 2,342

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- Definition Amortized cost of 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://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details
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