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Amortized Cost and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands | Jun. 26, 2021 | Dec. 26, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 170,095 | $ 119,013
Gross Unrealized Gains | 2,690 | 3,676
Gross Unrealized Losses | 238 | 98
Fair Value | 172,547 | 122,591
Money market investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 24,649 | 17,867
Fair Value | 24,649 | 17,867
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 564 | 567
Gross Unrealized Losses |  | 26
Fair Value | 564 | 541
Corporate bonds and direct obligations of government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 142,542 | 98,241
Gross Unrealized Gains | 2,602 | 3,551
Gross Unrealized Losses | 238 | 72
Fair Value | 144,906 | 101,720
U.S. Treasury obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,340 | 2,338
Gross Unrealized Gains | 88 | 125
Fair Value | $ 2,428 | $ 2,463

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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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